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Books and book chapters


203) Let There be Light: Polymeric Micelles with Upper Critical Solution Temperature as Light-Triggered Heat Nanogenerators for Combating Drug- Resistant Cancer

Author(s): Deng, Y.; Käfer, F.; Chen, T.; Jin, Q.; Ji, J.; Agarwal, S. Source: small, Vol. 14, 1802420, DOI: 10.1002/smll.201802420 Published: 2018

Abstract: Complete drug release and efficient drug retention are two critical factors in reversing drug resistance in cancer therapy. In this regard, polymeric micelles with an upper critical solution temperature (UCST) are designed as a new exploration to reverse drug resistance. The amphiphilic UCST‐type block copolymers are used to encapsulate photothermal agent IR780 and doxorubicin (DOX) simultaneously. The integrated UCST‐type drug nanocarriers show light‐triggered multiple synergistic effects to reverse drug resistance and are expected to kill three birds with one stone: First, owing to the photothermal effect of IR780, the nanocarriers will be dissociated upon exposure to laser irradiation, leading to complete drug release. Second, the photothermal effect‐induced hyperthermia is expected to avoid the efflux of DOX and realize efficient drug retention. Last but not least, photothermal ablation of cancer cells can be achieved after laser irradiation. Therefore, the UCST‐type drug nanocarriers provide a new strategy in reversing drug resistance in cancer therapy.


202) pH-Responsive Biohybrid Carrier Material for Phenol Decontamination in Wastewater

Author(s): Pretscher, M.; Pineda-Contreras, B.A.; Kaiser, P.; Reich, S.; Schöbel, J.; Kuttner, C.; Freitag, R.; Fery∥, A.; Schmalz, H.; Agarwal, S. Source: Biomacromolecules, Vol. 19, Pages: 3224-3232, DOI: 10.1021/acs.biomac.8b00361 Published: 2018

Abstract: Smart polymers are a valuable platform to protect and control the activity of biological agents over a wide range of conditions, such as low pH, by proper encapsulation. Such conditions are present in olive oil mill wastewater with phenol as one of the most problematic constituents. We show that elastic and pH-responsive diblock copolymer fibers are a suitable carrier for Corynebacterium glutamicum, i.e., bacteria which are known for their ability to degrade phenol. Free C. glutamicum does not survive low pH conditions and fails to degrade phenol at low pH conditions. Our tea-bag like biohybrid system, where the pH-responsive diblock copolymer acts as a protecting outer shell for the embedded bacteria, allows phenol degradation even at low pH. Utilizing a two-step encapsulation process, planktonic cells were first encapsulated in poly(vinyl alcohol) to protect the bacteria against the organic solvents used in the second step employing coaxial electrospinning.


201) Electrospun nanofiber reinforced composites: a review

Author(s): Jiang, S.; Chen, Y.; Duan, G.; Mei, C.; Greiner, A.; Agarwal, S. Source: Polym. Chem., Vol. 9, Pages: 2685-2720, DOI: 10.1039/C8PY00378E Published: 2018

Abstract: This paper provides a comprehensive overview on the properties of electrospun nanofibers and their application as reinforcements in composites. The paper first introduces the remarkable properties of electrospun nanofibers including high aspect ratio and molecular orientation, large specific surface area, small pore size, as well as excellent mechanical performance. Next the fabrication methods for the electrospun nanofiber reinforced composites are described. Then different kinds of electrospun nanofiber reinforced composites are discussed in terms of the classifications of electrospun nanofibers. After that, the influences of the mechanical performance of fibers, fiber diameter, fiber amount, fiber/matrix interfacial interaction and the distribution of fibers in the matrix on the reinforcement of composites are discussed. At the end, the possible future challenges and conclusions for electrospun nanofiber reinforced composites are highlighted.


200) Combining 3D printing with electrospinning for rapid response and enhanced designability of hydrogel actuators

Author(s): Chen, T.; Bakhshi, H.; Liu, L.; Ji, J.; Agarwal, S. Source: Adv. Funct. Mater., Vol. 28, 1800514, DOI: 10.1002/adfm.201800514 Published: 2018

Abstract: Porous structures have emerged as a breakthrough of shape-morphing hydro-gels to achieve a rapid response. However, these porous actuators generally suffer from a lack of complexity and diversity in obtained 3D shapes. Herein, a simple yet versatile strategy is developed to generate shape-morphing hydrogels with both fast deformation and enhanced designability in 3D shapes by combining two promising technologies: electrospinning and 3D printing. Elaborate patterns are printed on mesostructured stimuli-responsive electrospun membranes, modulating in-plane and interlayer internal stresses induced by swelling/shrinkage mismatch, and thus guiding morphing behav-iors of electrospun membranes to adapt to changes of the environment. With this strategy, a series of fast deformed hydrogel actuators are constructed with various distinctive responsive behaviors, including reversible/irrevers-ible formations of 3D structures, folding of 3D tubes, and formations of 3D structures with multi low-energy states. It is worth noting that although poly(N-isopropyl acrylamide) is chosen as the model system in the present research, our strategy is applicable to other stimuli-responsive hydrogels, which enriches designs of rapid deformed hydrogel actuators.


199) Composite polymeric membranes with directionally embedded fibers for controlled dual actuation

Author(s): Liu, L.; Bakhshi, H.; Jiang, S.; Schmalz, H.; Agarwal, S. Source: Macromol. Rapid Commun., Vol. 39. 1800082, DOI: 10.1002/marc.201800082 Published: 2018

Abstract: In this paper, preparation method and actuation properties of an innovative composite membrane composed of thermo‐ and pH‐responsive poly(N‐isopropylacrylamide‐co‐acrylic acid) fibers (average diameter ≈ 905 nm) embedded within a passive thermoplastic polyurethane (TPU) matrix at different angles with degree of alignment as high as 98% are presented. The composite membrane has a gradient of TPU along the thickness. It has the capability of temperature‐ and pH‐dependent direction‐, and size‐controlled actuation in few minutes. The stresses generated at the responsive fiber and nonresponsive matrix provide actuation, whereas the angle at which fibers are embedded in the matrix controls the actuation direction and size. The temperature has no effect on actuation and actuated forms at pH 7 and above, whereas the size of the actuated forms can be controlled by the temperature at lower pH. The membranes are strong enough to reversibly lift and release ≈426 times weight of their own mass (2.47 g metal ring is lifted by a 5.8 mg membrane). Soft actuators are of interest as smart scaffolds, robotics, catalysis, drug release, energy storage, electrodes, and metamaterials.


198) Ultraporous, compressible, wettable polylactide/polycaprolactone sponges for tissue engineering

Author(s): Mader, M.; Jérôme, V.; Freitag, R.; Agarwal, S.; Greiner, A. Source: Biomacromolecules, Vol. 19, Pages: 1663-1673, DOI: 10.1021/acs.biomac.8b00434 Published: 2018

Abstract: Ultraporous, degradable sponges made of either polylactide or of blends of polylactide/poly(ε-caprolactone) are prepared by freeze-drying of dispersions of short electrospun fibers and subsequent thermal annealing. The sponges feature ultrahigh porosity (99.6%), a hierarchical cellular structure, and high reversible compressibility with fast recovery from deformation in the dry as well as in the wet state. The sponge properties depend on the fiber dispersion concentration and the annealing temperature. Sponge characteristics like fiber density (2.5–20 mg/cm3), size, shape, crystallinity, mechanical strength, wetability, and structural integrity are user adjustable. Cell culture experiments were successfully performed with Jurkat cells with Confocal Laser Scanning Microscopy and MTT staining showing rapid cell proliferation. Live/Dead staining demonstrated high viability of the seeded cells. The sponge characteristics and modifications investigated and presented here reveal that these sponges are highly promising for tissue engineering applications.


197) Low density, thermally stable, and intrinsic flame retardant poly(bis(benzimidazo)benzophenanthrolinedione) sponge

Author(s): Zhu, J.; Jiang, S.; Hou, H.; Agarwal, S.; Greiner, A. Source: Macromol. Mater. Eng., Vol. 303, 1700615, DOI: 10.1002/mame.201700615 Published: 2018

Abstract: Low density (≤13.9 mg cm−3), compressible poly(bis(benzimidazo)benzophenanthroline-dione) (BBB) sponges with high temperature resistance are reported. The processing of BBB is limited due to its insolubility in organic solvents and infusibility. Therefore, the sponges are made in two steps: first, the BBB fibers are prepared by electrospinning the starting monomers with a template polymer followed by polycondensation of monomers on solid fibers at high temperature. In the second step, the BBB fibers are mechanically cut and self-assembled from a dispersion during freeze-drying. The use of poly(vinyl alcohol) is critical in getting self-assembled hierarchically double-pore-structured, mechanically stable sponges. The sponges show very high pyrolytic stability, high compressibility (more than 92% recovery after 50% compression), very low thermal conductivity (0.028–0.038 W mK−1), and high oil absorption capacity.


196) Low-Density Self-Assembled Poly(N-Isopropyl Acrylamide) Sponges with Ultrahigh and Extremely Fast Water Uptake and Release

Author(s): Jiang, SH (Jiang, Shaohua); Helfricht, N (Helfricht, Nicolas); Papastavrou, G (Papastavrou, Georg); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema) Source: MACROMOLECULAR RAPID COMMUNICATIONS Volume: 39 Issue: 8 Article Number: 1700838 APR 2018

Abstract: Poly(N‐isopropyl acrylamide) (PNIPAM) hydrogels are well known for their temperature‐dependent water uptake and release. Hence, they are ideal candidates for water management applications. However, efficiency and rate of water uptake and release, respectively, have to be optimized. Here, highly stable 3D PNIPAM sponges that show a sufficiently low density and high specific pore volume, required for maximizing the amount and rate of water absorption‐desorption, are presented. They are prepared by a top‐down approach based on freeze‐drying a dispersion of short crosslinked PNIPAM fibers coated with crosslinked PNIPAM. The sponges have low densities (4.10–21.04 mg cm−3), high porosities >98%, and high specific pore volumes in the range of 47–243 cm3 g−1 depending on the concentration of the dispersions. The sponges absorb high amounts of water (≈7000%) at temperatures below the lower critical solution temperature (LCST) of PNIPAM and can release more than 80% of the absorbed water above the LCST in less than 2 min. Moreover, the water‐swollen sponges are reversibly foldable, can be confined to different shapes, and have compressive elastic modulus below 10 Pa. Hence, these spongy materials are of interest not only for water management but also for biomedical applications, smart textiles, and catalysis.  


195) Polymer nanofibre composite nonwovens with metal-like electrical conductivity

Author(s): Reich, S.; Burgard, M.; Langner, M.; Jiang, S.; Wang, X.; Agarwal, S.; Ding, B.; Yu, J.; Greiner, A. Source: npj Flexible Electronics Volume: 2:5, DOI: 10.1038/s41528-017-0018-5. Published: 2018

Abstract: Bendable and breathable polymer nanofibre nonwovens with metal-like electrical conductivity are required for lightweight electrodes and electric shielding design with applications in batteries, functional textiles, sensors, cars, aerospace, constructions, mobile phones, and medical devices. Metal-like conductivity in polymer nonwovens has not been achieved till now due to the limitation of the existing processing techniques. We show here, the metal-like electrical conductivity of 750,000 S/m in polyacrylonitrile (PAN), poly(ε-caprolactone) (PCL) nonwoven using very low content of silver nanowires (AgNW; 3.35 vol%). The key to the high conductivity was the homogenous distribution of AgNW in nonwoven made by wet-laid process using short electrospun fibre and AgNW dispersion. Above a threshold of 0.36 vol% AgNW, the conductivity of the nonwoven increased by seven orders of magnitude, which we attribute to the onset of percolation of the AgNW. Our nonwoven-AgNW composites show fast heating and cooling within a few seconds at a voltage of 1.1 V, which is in the range of portable devices. These composites are also breathable and bendable. The electrical conductivity was independent of the bending angle of the composite, which is important for applications mentioned above and would help other scientists to design new conductive materials in the future.


194) Spin-crossover iron(II) coordination polymer with fluorescent properties: correlation between emission properties and spin state

Author(s): Lochenie, C.; Schötz, K.; Panzer, F.; Kurz, H.; Maier, B.; Puchtler, F.; Agarwal, S.; Köhler, A.; Weber, B. Source: J. Am. Chem. Soc. Volume: 140 Pages: 700-709 Published: 2018

Abstract: A spin-crossover coordination polymer [Fe(L1)(bipy)]n (where L = a N2O22– coordinating Schiff base-like ligand bearing a phenazine fluorophore and bipy = 4,4′-bipyridine) was synthesized and exhibits a 48 K wide thermal hysteresis above room temperature (T1/2↑ = 371 K and T1/2↓ = 323 K) that is stable for several cycles. The spin transition was characterized using magnetic measurements, Mössbauer spectroscopy, and DSC measurements. T-dependent X-ray powder diffraction reveals a structural phase transition coupled with the spin transition phenomenon. The dimeric excerpt {(μ-bipy)[FeL1(MeOH)]2}·2MeOH of the coordination polymer chain crystallizes in the triclinic space group P1̅ and reveals that the packing of the molecules in the crystal is dominated by hydrogen bonds. Investigation of the emission properties of the complexes with regard to temperature shows that the spin crossover can be tracked by monitoring the emission spectra, since the emission color changes from greenish to a yellow color upon the low spin-to-high spin transition.



193) Nanofibre preparation of non-processable polymers by solid-state polymerization of molecularly self-assembled monomers

Author(s): Zhu, J.; Ding, Y.; Agarwal, S.; Greiner, A. Source: Nanoscale Volume: 9 Pages: 18169-18174 Published: 2017

Abstract: Polybisbenzimidazobenzophenanthroline-dione (BBB) is a high-performance polymer which is characterized by very high mechanical strength in combination with exceptional thermal stability, but it cannot be processed to electrospun fibres for any useful applications due to its insolubility and infusibility. We overcame all obstacles in the electrospinning of BBB by a new bottom-up, and facile approach for the solid-state polymerization of self-assembled monomer precursors. Key to this new strategy is the incorporation of a high molecular weight sacrificial polymer to aid in fibre formation. The resulting electrospun BBB fibres and belts prepared thereof according to this new approach are very strong and show excellent thermal stability. We envisage that this procedure could be applied to other classes of non-processable high-performance polymers for the preparation of electrospun fibres for applications such as filtration, sound insulation, battery separation, electrodes, fire protection, and reaction engineering under demanding conditions.


192) Exploration of the electrical conductivity of double-network silver nanowires/polyimide porous low-density compressible sponges

Author(s): Jiang, S.; Reich, S.; Uch, B.; Hu, P.; Agarwal, S.; Greiner, A. Source: Appl. Mater Interfaces Volume: 9 Pages: 34286-34293 Published: 2017

Abstract: Stress-responsive, highly flexible, and breathable nanocomposite sponges show an electrical conductivity from 1.7 to 166.6 S/cm depending on the applied stress. Key for the responsive electrical conductivity of the sponges is the change of percolation of the silver nanowires. These sponges made of short electrospun fibers and silver nanowires could be applied without any amplifier for the operation of automobile bulbs and as an efficient Joule heater. The time required for electric heating (current on) and cooling is very short. Interestingly, the maximum temperature reached by electric heating depends on the compression status. The higher the compression status, the lower is the maximum temperature, which is in accordance with the understanding of Joule heaters. It is noteworthy that these sponges are thermally, chemically, and mechanically very stable. These conductive sponges will open a new area for novel conductive devices with relevance for real-world applications.


191) Ultralight, thermally insulating, compressible polyimide fiber assembled sponges

Author(s): Jiang, S.; Uch, B.; Agarwal, S.; Greiner, A. Source: ACS Appl. Mater. Interfaces Volume: 9 Pages: 32308-32315 Published: 2017

Abstract: Tunable density, thermally and mechanically stable, elastic, and thermally insulating sponges are required for demanding applications. Hierarchically structured sponges with bimodal interconnected pores, porosity more than 99%, and tunable densities (between 7.6 and 10.1 mg/cm3) are reported using polyimide (PI) as high temperature stable polymer. The sponges are made by freeze-drying a dispersion of short PI fibers and precursor polymer, poly(amic acid) (PAA). The concept of “self-gluing” the fibrous network skeleton of PI during sponge formation was applied to achieve mechanical stability without sacrificing the thermal properties. The sponges showed initial degradation above 400 and 500 °C in air and nitrogen, respectively. They have low thermal conductivity of 0.026 W/mK and thermal diffusivity of 1.009 mm2/s for a density of 10.1 mg/cm3. The sponges are compressible for at least 10 000 cycles and good thermal insulators even at high compressions. These fibrous PI sponges are promising candidates for potential applications in thermal insulation, lightweight construction, high-temperature filtration, sensors, and catalyst carrier for high-temperature reactions.


190) Exploration of macroporous polymeric sponges as drug carriers

Author(s): Duan, G.; Bagheri, A.; Jiang, S.; Golenser, J.; Agarwal, S.; Greiner, A. Source: Biomacromolecules, Vol. 18, Pages: 3215-3221, DOI: 10.1021/acs.biomac.7b00852

Abstract: Achieving high drug loading capacity and controlling drug delivery are two main challenges related to drug carriers. In this study, polymeric macroporous sponges with very high pore volume and large porosity are introduced as a new-type of drug carrier. Due to the high pore volume (285 and 166 cm3/g for the sponges with densities of 3.5 and 6.0 mg/cm3, respectively), the sponges exhibit very high drug loading capacities with average values of 1870 ± 114 and 2697 ± 73 mg/g in the present study, which is much higher than the meso and microporous drug carriers (<1500 mg/g). In order to control the release profiles, an additional poly(p-xylylene) (PPX) coating was deposited by chemical vapor deposition on the drug loaded sponge. Consequently, Artemisone (ART) release in the aqueous medium could be retarded, depending on the density of the sponge and the thickness of the coating. In future, the new 3D polymeric sponges would be highly beneficial as drug carriers for the programmed release of drugs for treatment of chronic diseases.


189) Hyperbranched polyesters as biodegradable and antibacterial additives

Author(s): Bakhshi, H.; Agarwal, S. Source: J. Mater. Chem. B, Vol. 5, Pages: 6827-6834, DOI: 10.1039/C7TB01301A Published: 2017

Abstract: Herein, we present novel hyperbranched poly(amino-ester)s functionalized with quaternary ammonium salts (QAS-HPAEs). These materials can be used as antibacterial and biodegradable additives for mixing with non-active polymers. The chemical structure and thermal properties of the HPAEs were studied. All QAS-HPAEs were stable until 192 °C, which makes their thermal blending with other polymers possible. Blending polycaprolactone (PCL) as a biodegradable polymer with QAS-HPAEs improved its surface and bulk hydrophilicity, while partially decreasing its elastic modulus and tensile strength. Mixing 10 wt% of QAS-HPAEs in PCL resulted in a film with high contact-killing activity against E. coli and B. subtilis and faster degradability in the presence and absence of esterase. The activity of esterase was inhibited in the presence of a higher content of QAS-HPAEs (20 wt%).


188) Tailoring the morphology of responsive bioinspired bicomponent fibers

Author(s): Gernhardt, M.; Peng, L.; Burgard, M.; Jiang, S.; Förster, B.; Schmalz, H.; Agarwal, S. Source: Macromol. Mater. Eng., Vol. 303, 1700248, DOI: 10.1002/mame.201700248 Published: 2017

Abstract: Nature is an intriguing inspiration for designing a myriad of functional materials. However, artificial mimicking of bioinspired structures usually requires different specialized procedures and setups. In this study, a new upscalable concept is presented that allows to produce two bioinspired, bicomponent fiber morphologies (side-by-side and coaxial bead-on-string) using the same electrospinning setup, just by changing the employed spinning solvent. The generated fiber morphologies are highly attractive for thermoresponsive actuation and water harvesting. Another challenge solved in this work is the compositional characterization of complex fiber morphologies. Raman imaging and atomic force microscopy is introduced as a powerful method for the unambiguous characterization of complex bicomponent fiber morphologies. The work opens the way for the construction of heterostructured fiber morphologies based on different polymers combinations, offering high potential for applications as actuators, smart textiles, water management, drug release, and catalysis.


187) Fate of so-called biodegradable polymers in seawater and freshwater

Author(s): Bagheri, A.; Laforsch, C.; Greiner, A.; Agarwal, S. Source: Global Challenges, Vol. 1, 170048, DOI: 10.1002/gch2.201700048 Published: 23. June 2017

Abstract:  The stability of polymers with C[BOND]C and stable C[BOND]heteroatom backbones against chemicals, hydrolysis, temperature, light, and microbes has challenged society with the problem of accumulation of plastic waste and its management worldwide. Given careless disposal of plastic waste, large amounts of plastic litter accumulate in the environment and disintegrate into microplastics. One of the questions frequently raised in the recent times is if so-called biodegradable polymers can substitute conventional polymers for several applications and help to tackle this challenge. The answer is not so simple as biodegradability is a certified property occurring only under certain environmental conditions and therefore requires systematic study. As a first step, this study focusses on comparative degradation studies of six polymers (five taken from the so-called biodegradable polyesters, including poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), polylactic acid (PLA), poly(3-hydroxybutyrate) (PHB), Ecoflex, and one well-known non-degradable polymer poly(ethylene terephthalate) (PET) in artificial seawater and freshwater under controlled conditions for 1 year. Only amorphous PLGA shows 100% degradation as determined by weight loss, change in molar mass with time, NMR, electron microscopy, and high-performance liquid chromatography. This is a step forward in understanding the degradability of polyesters required for the design of environmentally friendly novel polymers for future use.


186) Low-density open cellular sponges as functional materials

Author(s): Jiang, S.; Agarwal, S.; Greiner, A. Source: Angew. Chem. Int. Ed., Vol. 56, Pages: 15520-15538, DOI: 10.1002/anie.201700684 Published: 2017

Abstract: Low density macroporous sponges with densities less than 100 mg cm-3 are a challenge and an opportunity in advanced chemistry and material science. The challenge lies in the precise preparation of the sponges with property combinations that lead to novel applications. Bottom-up and top-down chemical and engineering methods for preparation are a major focus of this review, with an emphasis on carbon and polymer materials. Light weight, sustainability, breathability, special wetting characteristics, large mass transfer, mechanical stability, and large pore volume are typical characteristics of sponges made of advanced materials and could lead to novel applications. Some selected sponge properties and potential applications are discussed.


185) Poly(amino acid)-based gel fibers with pH responsivity by coaxial reactive electrospinning

Author(s): Molnar, K.; Jedlovszky-Hajdu, A.; Zrinyi, M.; Jiang, S.; Agarwal, S.; Source: Macromol. Rapid Commun., Vol. 38, 1700147, DOI: 10.1002/marc.201700147 Published: 2017

Abstract: Electrospinning is a well-known technique for the preparation of scaffolds for biomedical applications. In this work, a continuous electrospinning method for gel fiber preparation is presented without a spinning window. As proof of concept, the preparation of poly(aspartic acid)-based hydrogel fibers and their properties are described by using poly(succinimide) as shell polymer and 2,2,4(2,4,4)-trimethyl-1,6-hexanediamine as cross-linker in the core of the nozzle. Cross-linking takes place as the two solutions get in contact at the tip of the nozzle. The impact of solution concentrations and feeding rates on fiber morphology, proof of the presence of cross links as well as pH sensitivity after the transformation of the poly(succinimide)-based material to poly(aspartic acid) is presented.


184) Biobased polycarbonate as a gas separation membrane and "breathing glass" for energy saving applications

Author(s): Hauenstein, O.; Rahman, Md. M.; Elsayed, M.; Krause-Rehberg, R.; Agarwal, S.; Abetz, V.; Greiner, A. Source: Adv. Mater. Technol., Vol. 2, 1700026, DOI: 10.1002/admt.201700026 Published: 2017

Abstract: The biobased poly(limonene carbonate) (PLimC) synthesized by catalytic copolymerization of trans-limonene oxide and CO2 unifies sustainability, carbon capture and utilization of CO2 in one material. Films of PLimC show surprisingly high gas permeation and good selectivity. Additionally, it is not only very permeable to gases, but also to light, while simultaneously being a good heat insulator and mechanically strong, representing a novel type of material that is defined here as “breathing glass.” Hence, this study investigates the gas permeation and the selectivity in detail. The selectivity of PLimC for CO2 can be understood by its high fractional free volume, which is determined by positron annihilation lifetime spectroscopy supported by simulations. The CO2 permeability of PLimC at 30 °C is 68 barrer, while the CO2/N2 selectivity is ≈19, which places PLimC in a promising position in the Robeson plot and makes it unique due to its excellent transparency and processability under ambient conditions. Based on the high permeability of PLimC to gases and light, this study discusses here a completely new potential application of light transparent, gas-permeable polymer films as “breathing glass.”


183) Compaction and transmembrane delivery of pDNA: differences between I-PEI and two types of amphiphilic block copolymers.

Author(s): Raup, A.; Wang, H.; Synatschke, C. V.; Jérôme, V.; Agarwal, S.; Pergushov, D. V.; Müller, A.; Freitag, R. Source: Biomacromolecules Volume: 18 Issue: 3 Pages: 808-818 DOI: 10.1021/acs.biomac.6b01678

Abstract: Polycations are popular agents for nonviral delivery of DNA to mammalian cells. Adding hydrophobic, biodegradable, or cell-penetrating functions could help to improve their performance, which at present is below that of viral agents. A crucial first step in gene delivery is the complexation of the DNA. The characteristics of these “polyplexes” presumably influence or even determine the subsequent steps of membrane passage, intracellular traveling/DNA release, and nuclear uptake. Herein, polyplexes formed with linear poly(ethylenimine) (l-PEI) are compared to complexes generated with functionalized diblock copolymers. While l-PEI interacts only electrostatically with the DNA, interaction in the case of the diblock polymers may be mixed-mode. In certain cases, transfection efficiency improved when the polyplexes were formed in hypertonic solution. Moreover, whereas conventional PEI-based polyplexes enter the cells via endocytosis, at least one of the diblock agents seemed to promote entry via transient destabilization of the plasma membrane.


182) Self-rolled porous hollow tubes made up of biodegradable polymers.

Author(s): Peng, L.; Zhu, J.; Agarwal, S. Source: Macromol. Rapid Commun., Vol. 38, 1700034, DOI: 10.1002/marc.201700034 Published: 2017

Abstract: A tubular highly porous scaffold of polylactide (PLA) and poly-ε-caprolactone (PCL) is fabricated by self-rolling of a 2D fibrous bilayer of PLA and PCL in water without use of any classical thermo-/pH-responsive polymers. The self-rolling and diameter of the tube are dependent upon the bilayer thickness and temperature. A 75 µm thick 2D bilayer (PLA = 25 µm; PCL = 50 µm) rolls to a hollow tube of diameter around 0.41 mm with multilayered wall at 40 °C within 5 min. The tubes keep their form and size in water at all temperatures once they are formed. The interesting properties of the hollow tubes, that is, permeation of gases through the walls and flow of water without leakage under tested conditions in combination with good mechanical stability, use of only biodegradable polymers, and easy and reproducible fabrication method, allow them to be promising candidates for future studies as scaffolds for tissue engineering.


181) Unlocking nanocarriers for the programmed release of antimalarial drugs.

Author(s): Bagheri, A.; Agarwal, S.; Golenser, J.; Greiner, A. Source: Global Challenges Volume: 1 Issue: 2, 1600011, DOI: 10.1002/gch2.201600011 Published: FEB 2017

Abstract: A programmable release system with wide range of release profiles of the antimalarial artemisone (ART) from fibrous nanocarriers (NFN) is presented. This is achieved following a new paradigm of using ART-loaded NFN in infusion system of hydrophobic drug eluting nanocarriers, adapted to clinical applications. Very importantly, under these conditions ART did not degrade as it was observed in solution. 



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180) Tunable, concentration-independent, sharp, hysteresis-free UCST phase transition from poly(N-acryloyl glycinamide acrylonitrile) system.

Author(s): Käfer, F.; Lerch, A.; Agarwal, S. Source: Journal of Polymer Science, Part A: Polymer Chemistry Volume: 55 Issue: 2 Pages: 274-279 DOI: 10.1002/pola.28374 2016

Abstract: Poly(N-acryloylglycinamide-co-acrylonitrile) (poly(NAGA-AN)) copolymers were synthesized using reversible-addition-fragmentation transfer polymerization. In contrast to poly(NAGA) the thermoresponsive behavior of poly(NAGA-AN) shows a narrow cooling/heating hysteresis in water with a tunable cloud point, depending on the acrylonitrile amount in polymer. Furthermore, we showed that there is no significant effect of the solution concentration on the cloud point and stable phase transition behavior in electrolyte solutions, which is presumable controlled by forming stable micellar like structures as a result of the block/graft-copolymer structure. This is in contrast to poly(NAGA) which shows a strong concentration dependent cloud point in aqueous solution with a broad cooling/heating hysteresis.


179) One-component dual actuation: poly(NIPAM) can actuate to stable 3D forms with reversible size change.

Author(s): Liu, L.; Ghaemi, A.; Gekle, S.; Agarwal, S. Source: Advanced Materials Volume: 28 Issue: 44 Pages: 9792-9796 DOI: 10.1002/adma.201603677 2016

Abstract: The work provides a rare example of a one-component dual actuator with irreversible change in shape by rolling on contact with water and reversible size change on changing the temperature. The actuator has a bilayer structure with aligned and randomly oriented fibers of poly (N-isopropyl acrylamide). A combination of anisotropic E modulus and temperature dependent swelling/shrinkage provides the dual actuation.


178) Polyimide nanofibers by "green" electrospinning via aqueous solution for filtration applications.

Author(s): Jiang, SH (Jiang, Shaohua); Hou, HQ (Hou, Haoqing); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas) Source: ACS SUSTAINABLE CHEMISTRY & ENGINEERING Volume: 4  Issue: 9  Pages: 4797-4804  DOI: 10.1021/acssuschemeng.6b01031  Published: SEP 2016 
Abstract: The use of large amounts of environmentally unfriendly, toxic, and flammable organic solvents in electrospinning of polymers puts demand on the development of new methods and formulations for making water stable hydrophobic nanofibers from water-soluble precursor solution. Electrospun polyimide (PI) nanofibers are of particular interest for a variety of applications due to their extraordinary thermal and chemical stability. However, the intermediate precursor of polyimide, the polyamic acid (PAA) has to be electrospun from harmful solvents like dimethylformamide (DMF) which is a serious obstacle for technical applications of electrospun PI. This work highlights the formation of PI nanofibers by "green" electrospinning of ammonium salts of PAA from water. The high temperature used for imidization in the second step also removed ammonia and the template polymer by sintering giving PI nanofibers with diameter 295 +/- 58 nm. The thus obtained PI nanofibers by "green" electrospinning were defined as "green" PI nanofibers. Aerosol filtration of "green" PI nanofibers showed a performance that was very similar to PI nanofibers obtained by electrospinning of PAA from DMF. Additionally, it has been shown that the "green" PI nanofibers were suitable for the filtration of hot oil as well.


177) Assembly of gold nanoparticles on gold nanorods using functionalized poly(n-isopropylacrylamide) as polymeric "glue".

Author(s): Fan, ZY (Fan, Ziyin); Tebbe, M (Tebbe, Moritz); Fery, A (Fery, Andreas); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas) Source: PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION  Volume: 33  Issue: 9  Pages: 698-702  DOI: 10.1002/ppsc.201600081  Published: SEP 2016

Abstract: A telechelic thermoresponsive polymer, α-amino-ω-thiol-poly(N-isopropylacrylamide) (H2N-PNiPAM-SH), is used as the polymeric glue to assemble gold nanoparticles (AuNPs) around gold nanorods (AuNRs) into a satellite structure. Prepared by reversible addition-fragmentation chain transfer polymerization followed by hydrazinolysis, H2N-PNiPAM-SH is able to interlink the two types of the gold building blocks with the thiol-end grafting on AuNRs and the amine-end coordinating on the AuNP surface. The density of the grafted AuNPs on AuNRs can be tuned by adjusting the molar ratio between AuNPs and AuNRs in the feed. The resulted satellite-like assembly exhibits unique optical property that was responsive to temperature change.


176) Dendrons as active clicking tool for generating non-leaching antibacterial materials.

Author(s): Bakhshi, H (Bakhshi, Hadi); Agarwal, S (Agarwal, Seema) Source: POLYMER CHEMISTRY Volume: 7  Issue: 33  Pages: 5322-5330  DOI: 10.1039/c6py01105e  Published: 2016  
Abstract: We show a novel concept of using dendrons as a tool for making non-active materials antibacterial in a simple way. A dendron is a part of a dendrimer with the advantage of having many peripheral functional groups and a focal point. We used this structural advantage in making an antibacterial polymeric tool for clicking to other non-active polymers and surfaces. We show the success of the concept by making new antibacterial poly(urethane-biuret) dendrons containing quaternary ammonium salts (QASs) on the periphery and a primary hydroxyl group as the focal point in one pot. The chemical structure and thermal properties of the dendrons were fully studied. All quaternized dendrons were stable until above 200 degrees C. The newly synthesized dendrons show high activity against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) as tested by the determination of MIC, MBC values and the Kirby-Bauer assay. The hydroxyl group enabled the attachment of the dendrons to a cotton mat and PU foam, as a reactive additive, bringing them non-leaching fast bactericidal activity. The interaction of urethane and biuret bonds in the dendrons' backbone led to a transparent non-leaching bactericidal coating on the treated glass slides.


175) Structural exploration of phantom oligoguanidine from asymmetric diamine and guanidine hydrochloride.

Author(s): Wang, H (Wang, Hui); Bethke, C (Bethke, Christian); Hermann, M (Hermann, Markus); Frenking, G (Frenking, Gernot); Agarwal, S (Agarwal, Seema) Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 217  Issue: 16  Pages: 1834-1841  DOI: 10.1002/macp.201600154  Published: AUG 2016

Abstract: Condensation reaction of asymmetric triamine (spermidine) with guanidine hydrochloride provides a phantom structure with selective formation of rings in the repeat unit. The intermolecular condensation between amine and guanidine hydrochloride can provide either a linear structure or six- or seven-membered rings in the repeat unit by elimination of one or three molecules of ammonia, respectively, per repeat unit. The preference of formation of rings and mechanistic aspects are studied by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 1D, 2D NMR, and quantum chemical calculations.


174) Buckling and unraveling poly(n-isopropyl acrylamide)-thermoplastic polyurethane bilayers.

Author(s): Yarin, A.; Agarwal, S. Source: Polymer Volume: 97 Pages: 604-613 DOI: 10.1016/j.polymer.2016.05.057 2016

Abstract: The theory of two-dimensional Poly(N-isopropyl acrylamide)-Thermoplastic Polyurethane (PNIPAM-TPU) bilayers and of three-dimensional PNIPAM-TPU bilayer filaments is developed. This is the first theory which provides a comprehensive explanation and a detailed description of buckling of PNIPAM-TPU bilayers, as to our knowledge. In agreement with the experimental evidence it reveals that being immersed in a water bath at temperature T < LCST (the lower critical solution temperature), water infiltration into the porous PNIPAM layer of the bilayer begins resulting in swelling and stretching. Being inevitably perturbed (not perfectly straight) at the beginning, a long thin bilayer begins to buckle. However, its buckling is not identical to that of the elastic Euler bars, since the PNIPAM layer in the bilayer is loaded by a distributed compressive force imposed by the bonded TPU layer, while the Euler bars are loaded by compressive forces only at the ends. It is shown that when buckling bilayer stays in the cold bath at T < LCST for a long enough time, its stretching practically stops. However, its buckling continues for a while, since the longitudinal compressive force acting on the PNIPAM layer from the bonded TPU layer permanently exists. That results in self-coiling of the bilayer, which continues until a steady-state coiled configuration is achieved. It is shown that the steady-state coil radius is of the order of the bilayer thickness, much less than the original bilayer length, because the bilayer buckling is driven by a longitudinally distributed compressive force rather than by the compressive force applied only at the ends (like in the classical Euler buckling when the final radius of curvature is of the order of the bar length). If alternatively, after some period of swelling, stretching and buckling, water in the bath is replaced by hot water at T > LCST, water outflow from the PNIPAM-TPU bilayer begins and it shrinks to its original short length and a practically straight initial configuration. When a PNIPAM-TPU bilayer is immersed directly in a water bath at T > LCST, the PNIPAM layer begins to shrink, thus compressing the TPU layer, which in turn, triggers buckling. Long PNIPAM-TPU bilayer filaments, being submerged in water bath at T < LCST, buckle as a circular helix with its radius of curvature and pitch decreasing in time.


173) Bio-based polycarbonate as synthetic toolbox.

Author(s): Hauenstein, O; Agarwal, S; Greiner, A Source: Nature communications Volume: 7 Pages: 11862
DOI: 10.1038/ncomms11862 Published: 2016 Jun 15
Abstract: Completely bio-based poly(limonene carbonate) is a thermoplastic polymer, which can be synthesized by copolymerization of limonene oxide (derived from limonene, which is found in orange peel) and CO2. Poly(limonene carbonate) has one double bond per repeating unit that can be exploited for further chemical modifications. These chemical modifications allow the tuning of the properties of the aliphatic polycarbonate in nearly any direction. Here we show synthetic routes to demonstrate that poly(limonene carbonate) is the perfect green platform polymer, from which many functional materials can be derived. The relevant examples presented in this study are the transformation from an engineering thermoplastic into a rubber, addition of permanent antibacterial activity, hydrophilization and even pH-dependent water solubility of the polycarbonate. Finally, we show a synthetic route to yield the completely saturated counterpart that exhibits improved heat processability due to lower reactivity. 


172) Biodegradable aliphatic-aromatic polyester with antibacterial property.

Hui Wang, Markus Langner, Seema Agarwal Source: Polymer Engineering and Science Volume: 56 Issue: 10 Pages: 1146-1152 Published: 2016, DOI: 10.1002/pen.24347

Abstract: Fast acting antibacterial property was introduced to aliphatic–aromatic polyester in the present work without sacrificing its compostability, thermal stability, and mechanical properties. Antibacterial poly(hexamethylene guanidine) hydrochloride (PHMG) was melt mixed with poly(butyleneadipate-co-terephthalate) (PBAT, also called Ecoflex) using a twin-screw extruder in different amounts. The non-reactive blending and uniform mixing was confirmed by nuclear magnetic resonance, gel permeation chromatography, scanning electron microscopy, and energy-dispersive X-Ray spectroscopy analysis. The influence of antibacterial agent on compostability, mechanical properties, and thermal stability was studied. The presence of PHMG changed slightly the degradation profile of Ecoflex retaining the extent of degradation almost the same. The antibacterial PBAT showed high thermal stability (degradation starts around 330°C), stress at break 17–20 MPa, modulus 89–127 MPa, and elongation at break more than 700% depending upon the amount of PHMG. The combination of antibacterial activity with biodegradability makes this material a very interesting candidate for many different applications including packaging. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers.


171) Protection of vine plants against Esca disease by breathable electrospun antifungal nonwovens.

Viola Buchholz, Melanie Molnar, Hui Wang, Steffen Reich, Seema Agarwal, Michael Fischer, Andreas Greiner Source: Macromol. Biosci. Volume: 16 Issue: 9 Pages: 1391-1397 Published: 2016 DOI: 10.1002/mabi.201600118                                                                                                   Abstract: The harmful Esca disease in vine plants caused by wood-inhabiting fungi including Phaeomoniella chlamydospora (Pch) is spreading all across the world. This disease leads to poor vine crops and a slow decline or to a sudden dieback of the vine plants. The pruning wounds of vine plants are the main entry point for Pch. While model experiments with aerosol particles recommend electrospun nonwovens as a suitable barrier to block Pch, tests with living spores show clearly that only electrospun fibrous nonwovens do not prevent Pch invasion. However it is found, that with antifungal additives electrospun nonwovens could be applied successfully for blocking of Pch to infect the substrate. Thereby, a highly useful concept for the protection of vine plants against Esca disease is provided which could also serve as a concept for related plant diseases. 


170) Photo-polimerizable, low shrinking modular construction kit with high efficiency based on vinylcyclopropanes.

Author(s): Contreras, PP (Contreras, Paul Pineda); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 7  Issue: 18  Pages: 3100-3106  DOI: 10.1039/c6py00411c  Published: 2016  
Abstract: The successful development of a universal hydrogen bond (H-bond) concept, specific for bi-functional vinylcyclopropane (VCP) ester-amide derivatives is reported here. Thereby, uniformity within the intermolecular hydrogen bond strength as investigated by variable temperature NMR and FT-IR measurements provides an excellent control of high reactivity, nearly regardless of the chosen spacer-unit, offering the system a possible application as a modular construction kit for cross-linked networks with varied properties. Two entirely diversified VCP ester-amide systems were prepared. The performance benchmark of a flexible, high molar mass macro-monomer VCPPPG(2000), implementing a polypropyleneglycol Genamine D01/2000 macro-spacer, and two rigid, low molar mass monomers VCP-m-phenyl and VCP-p-phenyl outlined significantly the strength of the system. Extremely low volume shrinkages between 1.4-4.5% and a wide range of E-moduli could be achieved. An easy control of adjusting final characteristics by varying the co-monomer content in co-networks was shown, especially without obtaining any significant disadvantage in the curing behavior. The VCP ester-amides offer the possibility to replace some currently used dimethacrylate resins within several high-end applications, especially where low volume shrinkage and high polymerization efficiency are required.


169) Ultralight open cell polymer sponges with advanced properties by PPX CVD coating.

Author(s): Duan, GG (Duan, Gaigai); Jiang, SH (Jiang, Shaohua); Moss, T (Moss, Tobias); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas) Source: POLYMER CHEMISTRY  Volume: 7  Issue: 15  Pages: 2759-2764  DOI: 10.1039/c6py00339g  Published: 2016  
Abstract: Ultralight polyacrylate sponges were prepared from dispersions of short electrospun polymer fibres by freeze drying and coated with poly(p-xylylene) (PPX) by chemical vapour deposition (CVD). The PPX coating of the sponges increased the compression strength, the water contact angle, and the solvent resistance significantly without significant alteration of the sponge morphology.


168) pH dependent thermoresponsive behavior of acrylamide-acrylonitrile UCST-type copolymers in aqueous media.

Author(s): Pineda-Contreras, BA (Pineda-Contreras, Beatriz A.); Schmalz, H (Schmalz, Holger); Agarwal, S (Agarwal, Seema) Source: POLYMER CHEMISTRY  Volume: 7  Issue: 10  Pages: 1979-1986  DOI: 10.1039/c6py00162a  Published: 2016  
Abstract: There are only a few non-ionic polymers known for showing thermoresponsivity of UCST-type. Copolymers of acrylamide (AAm) and acrylonitrile (AN) represent one of such thermoresponsive polymers. The present work shows pH-dependent UCST-transitions of this copolymer system. Herein, systematic studies were carried out to show hydrolytic stability and retention of UCST of the copolymer under various conditions. Regeneration of lost UCST-type transitions under extreme pH conditions could be achieved by changing pH, and by addition of electrolytes. Reversible addition fragmentation chain transfer (RAFT) was employed as a tool to synthesize copolymers of AAm and AN. Hydrolysis reactions were carried out intentionally under acidic and alkaline conditions, in order to analyze the chemical stability of the synthesized copolymers as well as to introduce carboxylic groups into the polymer structure. The obtained results showed high tolerance of poly(AAm-co-AN) samples under acidic conditions even after long periods of storage (25 days at pH 3) or after use of pH 0 and increased temperatures (40 degrees C). In the case of base catalyzed hydrolysis, the thermoresponsive behavior was significantly influenced during hydrolysis in buffer solution of pH 9. Loss and regeneration of the phase transition temperature of these copolymers could be achieved by changing the pH from basic to acidic. Meanwhile, hydrolysis at pH 14 at 40 degrees C influenced the thermoresponsive behavior and the chemical stability of the polymer, increasing the phase transition temperature over 30 degrees C. Further, we observed that additives, e.g. formamide can act as a sacrificial agent for providing stable UCST-type transitions even under alkaline conditions as well as at high temperatures (85 degrees C).


167) Quantitative comparison of the antimicrobial efficiency of leaching versus nonleaching polymer material.

By: Bruenke, J (Bruenke, Joerg); Roschke, I (Roschke, Ingolf); Agarwal, S (Agarwal, Seema); Riemann, T (Riemann, Thomas); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR BIOSCIENCE Volume: 16 Issue: 5 Pages: 647-654 DOI: 10.1002/mabi.201500266 Published: MAY 2016
Abstract: New antimicrobial materials will be more and more in the focus for hygienic and clinical disease control. Antimicrobial materials have to be distinguished in leaching and nonleaching materials. For many applications of antimicrobial materials on implants the use of nonleaching materials is essential. Therefore, the antimicrobial efficiency of leaching and nonleaching polymers has been investigated quantitatively in vitro in direct comparison on a highly relevant implant of central venous catheters (CVCs) using a well-established called Certika test. This test is especially designed to test antimicrobial properties of leachable and nonleachable materials. This contribution demonstrates that newly developed nonleaching antimicrobial CVCs are equivalent to conventional leaching CVC systems in their antimicrobial performance against gram-positive and gram-negative bacteria, as well as Candida species. The use of new nonleaching antimicrobial polymers as shown here for CVCs represents a different mode of action with the aim to prevent infections also with antibiotic-resistant strains and reduced side effects.


166) Two-in-One Composite Fibers With Side-by-Side Arrangement of Silk Fibroin and Poly(L-lactide) by Electrospinning.

Author(s): Peng, L (Peng, Ling); Jiang, SH (Jiang, Shaohua); Seuss, M (Seuss, Maximilian); Fery, A (Fery, Andreas); Lang, G (Lang, Gregor); Scheibel, T (Scheibel, Thomas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 301  Issue: 1  Pages: 48-55  DOI: 10.1002/mame.201500217  Published: JAN 2016  
Abstract: 1D fibers of Bombyx mori silk fibroin (SF) and poly(L-lactide) (SF-s-PLLA) with side-by-side parallel arrangement of the two components in a single fiber made by electrospinning are presented. The side-by-side arrangement in both randomly oriented and aligned two-in-one fibers was confirmed by scanning electron and confocal laser scanning microscope studies. The molecular orientation and secondary structure of SF and PLLA were dependent on the fiber alignment and annealing conditions. The two sides retained their individual secondary structure before and after annealing without affecting each other in a significant way. The two-in-one fibers after post treatment with methanol and heat at 80 degrees C showed tensile strength 16.5 +/- 1.4 MPa, modulus 205 +/- 20.6 MPa, and an elongation at break of 53 +/- 8%.

165) Bio-based Polycarbonate from Limonene Oxide and CO2 with High Molecular Weight, Excellent Thermal Resistance, Hardness and Transparency.

Author(s): Hauenstein, O (Hauenstein, O.); Reiter, M (Reiter, M.); Agarwal, S (Agarwal, S.); Rieger, B (Rieger, B.); Greiner, A (Greiner, A.)
Source: GREEN CHEMISTRY Volume: 18 Issue: 3 Pages: 760-770 DOI: 10.1039/c5gc01694k Published: 2016
Abstract: Completely bio-based, high molecular weight (>100 kDa) poly(limonene carbonate) (PLimC) with attractive thermal (glass transition temperature, T-g = 130 degrees C) and optical properties (transmission 94%, haze 0.75%) was prepared by coupling bio-based limonene oxide (LO) and carbon dioxide (CO2) using a beta-diiminate zinc catalyst (bdi)Zn(OAc). The molar mass of the polymer could be controlled by changing the ratio of catalyst and monomer, keeping molar mass dispersities low. The synthesis of the LO with very high content (> 85%) of trans-isomer and absence of impurities with hydroxyl functionality was also established, which was necessary to obtain a high molar mass of polymer and almost quantitative conversion of epoxide during polymerisation. The upscaled syntheses of both the monomer and the polymer (>1 kg per batch) were readily realised, suggesting an easy transfer to pilot plant scale. The polymerisation kinetics were studied suggesting a second order dependence on LO concentration, wherefrom a mechanism is proposed with an alternating insertion of LO and CO2. The effect of chain-ends on the thermal stability of PLimC was studied with a thermal desorption unit coupled with gas chromatography-mass spectrometry (GC-MS) experiments. PLimC with thermal stability as high as 240 degrees C could be achieved using appropriate end-capping agents. PLimC is characterised by excellent transparency and hardness.



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164) Giving Direction to Motion and Surface with Ultra-Fast Speed Using Oriented Hydrogel Fibers.

Author(s): Liu, L (Liu, Li); Jiang, SH (Jiang, Shaohua); Sun, Y (Sun, Yue); Agarwal, S (Agarwal, Seema) Source: ADVANCED FUNCTIONAL MATERIALS  Volume: 26  Issue: 7  Pages: 1021-1027  DOI: 10.1002/adfm.201503612  Published: FEB 16 2016  
Abstract: Thermoresponsive hydrogel fibrous membranes showing directionally controlled movements and surface change with ultra-fast speed are presented for the first time. They show reversible coiling, rolling, bending, and twisting deformations in different controllable directions for many cycles (at least 50 cycles tried) with inside-out change in surfaces and shapes. Speed, reversibility, large-scale deformations and, most importantly, control over the direction of deformation is required in order to make synthetic actuators inspired from natural materials or otherwise. A polymeric synthetic material combining all these properties is still awaited. This issue is addressed and provide a very simple system fulfilling all these requirements by combining porosity and asymmetric swelling/shrinking via orientation of hydrogel fibers at different angles in a fibrous membrane. Electrospinning is used as a tool for making membranes with fibers oriented at different angles.


163) Self-Organization of Gold Nanoparticle Assemblies with 3D Spatial Order and Their External Stimuli Responsiveness.

Author(s): Serrano, MSK (Serrano, Melissa S. Koehn); Konig, TAF (Koenig, Tobias A. F.); Haataja, JS (Haataja, Johannes S.); Lobling, TI (Lobling, Tina I.); Schmalz, H
(Schmalz, Holger); Agarwal, S (Agarwal, Seema); Fery, A (Fery, Andreas); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR RAPID COMMUNICATIONS Volume: 37 Issue: 3 Pages: 215-220 DOI: 10.1002/marc.201500509 Published: FEB 2016
Abstract: Gold nanoparticles (AuNP) with pyridyl end-capped polystyrenes (PS-4VP) as quasi-monodentate ligands self-assemble into ordered PS-4VP/AuNP nanostructures with 3D hexagonal spatial order in the dried solid state. The key for the formation of these ordered structures is the modulation of the ratio AuNP versus ligands, which proves the importance of ligand design and quantity for the preparation of novel ordered polymer/metal nanoparticle conjugates. Although the assemblies of PS-4VP/AuNP in dispersion lack in high dimensional order, strong plasmonic interactions are observed due to close contact of AuNP. Applying temperature as an external stimulus allows the reversible distortion of plasmonic interactions within the AuNP nanocomposite structures, which can be observed directly by naked eye. The modulation of the macroscopic optical properties accompanied by this structural distortion of plasmonic interaction opens up very interesting sensoric applications.


162) Synthesis and Enzymatic Degradation of Soft Aliphatic Polyesters.

Author(s): Buchholz, V (Buchholz, Viola); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR BIOSCIENCE Volume: 16 Issue: 2 Pages: 207-213 DOI: 10.1002/mabi.201500279 Published: FEB 2016
Abstract: Novel aliphatic enzymatically degradable polyesters with short alkyl side chains for tuning crystallinity are presented in this work. The intrinsic problem of aliphatic polyesters is their brittleness and tendency to crystallize. This was modulated by the synthesis of random copolyesters based on aliphatic linear monomers, adipic acid, 1,5-pentanediol and monomers with aliphatic branches, such as 2-butyl-2-ethyl-1,3-propanediol by polycondensation. The resulting copolyesters were crystalline, wax-like or had liquid texture with varied mechanical properties and enzymatic degradability depending upon the copolymer composition. Such polyesters are of significant interest for a wide range of possible applications such as controlled drug delivery, agricultural applications and as packing materials.


161) Enzymatically Degradable Polyester-Based Adhesives.

Author(s): Shi, YF (Shi, Yinfeng); Zhou, PR (Zhou, Peiran); Jerome, V (Jerome, Valerie); Freitag, R (Freitag, Ruth); Agarwal, S (Agarwal, Seema) Source: ACS BIOMATERIALS-SCIENCE & ENGINEERING  Volume: 1  Issue: 10  Pages: 971-977  DOI: 10.1021/acsbiomaterials.5b00217  Published: OCT 2015  
Abstract: A designed 3,4-dihydroxyphenylalanine (DOPA) mimetic enzymatic degradable synthetic adhesive with good adhesion to soft tissue and metals made by a simple two-step reaction is presented in this article. This adhesive has degradable polycaprolactone-type of repeat units together with glycidyl methacrylate (GMA) and oligo(ethylene glycol) methacrylate (OEGMA) on the polymer backbone. Radical initiated copolymerization of 2-methylene-1,3-dioxepane (MDO), glycidyl methacrylate (GMA) and OEGMA followed by immobilization of catechol group on epoxy rings of GMA provided the adhesive material. Fe(acac)3 was proved to be the most effective cross-linking agent with lap shear strength of 13.13 +/- 1.74 kPa and 218.4 +/- 16.0 kPa on soft tissue (porcine skin) and metal (aluminum), respectively. The cross-linked adhesive showed good adhesion stability in pH 7 PBS buffer at 37 degrees C for at least 1 week. Because of the high adhesive strength, enzymatic degradability, and low toxicity, the material is a promising candidate for future studies as medical glue.


160) Polymer Cages as Universal Tools for the Precise Bottom-Up Synthesis of Metal Nanoparticles.

Author(s): Fan, Z (Fan, Ziyin); Chen, X (Chen, Xuelian); Serrano, MK (Serrano, Melissa Kohn); Schmalz, H (Schmalz, Holger); Rosenfeldt, S (Rosenfeldt, Sabine); Forster, S (Foerster, Stephan); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION  Volume: 54  Issue: 48  Pages: 14539-14544  DOI: 10.1002/ange.201506415  Published: NOV 23 2015  
Abstract: A template synthesis allows the preparation of monodisperse nanoparticles with high reproducibility and independent from self-assembly requirements. Tailor-made polymer cages were used for the preparation of nanoparticles, which were made of cross-linked macromolecules with pendant thiol groups. Gold nanoparticles (AuNPs) were prepared in the polymer cages in situ, by using different amounts of cages versus gold. The polymer cages exhibited a certain capacity, below which the AuNPs could be grown with excellent control over the size and shape. Control experiments with a linear diblock copolymer showed a continuous increase in the AuNP size as the gold feed increased. This completely different behavior regarding the AuNP size evolution was attributed to the flexibility of the polymer chain depending on cross-linking. Moreover, the polymer cages were suitable for the encapsulation of AgNPs, PdNPs, and PtNPs by the in situ method.

159) Large Multipurpose Exceptionally Conductive Polymer Sponges Obtained by Efficient Wet-Chemical Metallization.

Author(s): Langner, M (Langner, Markus); Agarwal, S (Agarwal, Seema); Baudler, A (Baudler, Andre); Schroder, U (Schroeder, Uwe); Greiner, A (Greiner, Andreas)
Source: ADVANCED FUNCTIONAL MATERIALS  Volume: 25  Issue: 39  Pages: 6182-6188  DOI: 10.1002/adfm.201502636  Published: OCT 21 2015  
Abstract: Exceptionally conductive (250 S cm(-1)), very fast electrically heatable, thermally insulating, antimicrobial 3D polymeric sponges with very low density (approximate to 30 mg cm(-3)), superhydrophobicity, and high porosity, their method of preparation, and manifold examples for applications are presented here. The electrical heatability is reversible, reaching 90 degrees C with 4.4 W in about 19-20 s and cooling immediately on switching off the voltage. The sponges show high contact angles >150 degrees against water on the sponge surface as well as inside the sponge. Water droplets injected into the sponges are ejected. A facile wet-chemical method established for macroscopic melamine-formaldehyde sponges is the key for the thorough in-depth surface metallization of the sponges. The coating thickness and uniformity depend on the metallization formulation, conditions of metallization, and the type of metal used. A scanning electron microscope is used for morphology characterization. A reduced metallization rate in air is highly critical for the in-depth uniform coating of metals. The resulting metallized sponges could be highly interesting for heating as well as insulation devices in addition to oil/water separation membranes.

158) Unusual and Superfast Temperature-Triggered Actuators.

Author(s): Jiang, SH (Jiang, Shaohua); Liu, FY (Liu, Fangyao); Lerch, A (Lerch, Arne); Ionov, L (Ionov, Leonid); Agarwal, S (Agarwal, Seema)
Source: ADVANCED MATERIALS  Volume: 27  Issue: 33  Pages: 4865-4870  DOI: 10.1002/adma.201502133  Published: SEP 2 2015  
Abstract: A superfast actuator based on a bilayer fibrous mat shows folding/unfolding and the formation of 3D structures in a fraction of a second. The actuation is reversible for many cycles without losing its form and size, with unfolding at room temperature and folding above 35 degrees C. The system is promising for making 3D bioscaffolds, electrodes, and micro-/macroactuators.

157) LCST and UCST in One: Double Thermoresponsive Behavior of Block Copolymers of Poly(ethylene glycol) and Poly(acrylamide-co-acrylonitrile).

Author(s): Kafer, F (Kaefer, Florian); Liu, FY (Liu, Fangyao); Stahlschmid, U (Stahlschmid, Ullrich); Jerome, V (Jerome, Valerie); Freitag, R (Freitag, Ruth); Karg, M (Karg, Matthias); Agarwal, S (Agarwal, Seema)
Source: LANGMUIR  Volume: 31  Issue: 32  Pages: 8940-8946  DOI: 10.1021/acs.langmuir.5b02006  Published: AUG 18 2015  
Abstract: The change in thermoresponsive behavior from a single phase transition of upper critical solution temperature (UCST)-type of an acrylamide-acrylonitrile copolymer (AAm-co-AN) to a double responsive behavior (LCST-UCST-type (LCST, lower critical solution temperature)) in water by the introduction of a poly(ethylene glycol) (PEG) block is highlighted in the present work The polymer is synthesized in a simple way by free-radical polymerization of acrylamide and acrylonitrile using a poly(ethylene glycol) (PEG) macro-azoinitiator. The dual thermoresponsive behavior was observed in a wide range of concentrations repeatable for many cycles with very small hysteresis depending upon the ratio of AAm, AN and PEG. Static light scattering (SLS) and dynamic light scattering (DLS) together with turbidity photometry and transmission electron microscopy confirmed a unique phase transition behavior due to the temperature dependent change in the morphology from micelles to agglomerates. The low cytotoxicity and two-in-one thermoresponsive behavior makes the polymer promising for biomedical applications in the future.

156) Living Composites of Bacteria and Polymers as Biomimetic Films for Metal Sequestration and Bioremediation.
Author(s): Knierim, C (Knierim, Christian); Enzeroth, M (Enzeroth, Michaela); Kaiser, P (Kaiser, Patrick); Dams, C (Dams, Christian); Nette, D (Nette, David); Seubert, A (Seubert, Andreas); Klingl, A (Klingl, Andreas); Greenblatt, CL (Greenblatt, Charles L.); Jerome, V (Jerome, Valerie); Agarwal, S (Agarwal, Seema); Freitag, R (Freitag, Ruth); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 15  Issue: 8  Pages: 1052-1059  DOI: 10.1002/mabi.201400538  Published: AUG 2015  
Abstract: Herein, we report on composite materials of biologically active microorganisms placed in a synthetic polymer matrix. These so-called "living composites" were utilized for gold sequestration (Micrococcus luteus) and bioremediation of nitrite (Nitrobacter winogradskyi) to demonstrate functionality. For the preparation of the living composites the bacteria were first encased in a water-soluble polymer fiber (poly(vinyl alcohol), PVA) followed by coating the fibers with a shell of hydrophobic poly(p-xylylene) (PPX) by chemical vapor deposition (CVD). The combination of bacteria with polymer materials assured the stability and biologically activity of the bacteria in an aqueous environment for several weeks.

155) Thermally stable optically transparent copolymers of 2-methylene-1,3-dioxepane and N-phenyl maleimide with degradable ester linkages.

Author(s): Shi, YF (Shi, Yinfeng); Agarwal, S (Agarwal, Seema)
Source: E-POLYMERS  Volume: 15  Issue: 4  Pages: 217-226  DOI: 10.1515/epoly-2015-0096  Published: JUL 2015  
Abstract: The copolymers of 2-methylene-1,3-dioxepane (MDO) and N-phenyl maleimide (NPM) prepared by radical polymerization with high thermal stability, glass transition temperature and optical transparency are presented. The polymers made under specific reaction conditions, i.e., 120 degrees C and high amounts of MDO, had degradable ester units, which were formed via radical ring-opening polymerization of MDO. The formation of charge-transfer complex between MDO and NPM also led to the formation of high-molar-mass copolymers by simple mixing and heating of monomers without the use of any initiator. Structural characterization of the copolymers including mechanistic studies was carried out using nuclear magnetic resonance spectroscopy, and their thermal properties were studied using differential scanning calorimetry and thermogravimetric analysis.

154) Polymer/Nanoparticle Hybrid Materials of Precise Dimensions by Size-Exclusive Fishing of Metal Nanoparticles.

Author(s): Fan, ZY (Fan, Ziyin); Serrano, MK (Serrano, Melissa Koehn); Schaper, A (Schaper, Andreas); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: ADVANCED MATERIALS  Volume: 27  Issue: 26  Pages: 3888-+  DOI: 10.1002/adma.201501306  Published: JUL 8 2015  
Abstract: Polymer cages prepared by etching of gold nanoparticles from polymer templates by the "grafting around" method are designed for selective separation of metal nanoparticles. The separation process is demonstrated as a fast biphasic ligand exchange reaction. The high separation efficiency and size selectivity of the polymer cage is verified by comparison with the linear block copolymer.

153) Reversible gold nanorod alignment in mechano-responsive elastomers.

Author(s): Pletsch, H (Pletsch, Holger); Tebbe, M (Tebbe, Moritz); Dulle, M (Dulle, Martin); Forster, B (Foerster, Beate); Fery, A (Fery, Andreas); Forster, S (Foerster, Stephan); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: POLYMER  Volume: 66  Pages: 167-172  DOI: 10.1016/j.polymer.2015.04.037  Published: JUN 1 2015  
Abstract: Inspired by an increasing demand for stimuli-controlled assembly of nanostructures, mechano-responsive nanocomposites are designed with tremendous scope in material applications. Providing switchable properties by means of mechanical stimulation, elastomer-incorporated gold nanorods (AuNR) are presented herein. Stepless and reversible control over the orientational AuNR alignment and therefore over macroscopic anisotropy - is exerted by uniaxial film elongation. In context of optical applications, substantial impact on the plasmonic properties within adjustable spectral ranges is demonstrated. Mechano-responsive nanocomposites with high thermal colloidal stability are prepared via a facile hetero-phase ligand exchange procedure where complete coverage of the AuNR surface with hydrophobic ligands is achieved. (C) 2015 Elsevier Ltd. All rights reserved.

152) Ultralight, Soft Polymer Sponges by Self-Assembly of Short Electrospun Fibers in Colloidal Dispersions. Duan, G. Author(s): Duan, GG (Duan, Gaigai); Jiang, SH (Jiang, Shaohua); Jerome, V (Jerome, Valerie); Wendorff, JH (Wendorff, Joachim H.); Fathi, A (Fathi, Amir); Uhm, J (Uhm, Jaqueline); Altstadt, V (Altstaedt, Volker); Herling, M (Herling, Markus); Breu, J (Breu, Josef); Freitag, R (Freitag, Ruth); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: ADVANCED FUNCTIONAL MATERIALS  Volume: 25  Issue: 19  Pages: 2850-2856  DOI: 10.1002/adfm.201500001  Published: MAY 20 2015  
Abstract: Ultralight polymer sponges are prepared by freeze-drying of dispersions of short electrospun fibers. In contrast to many other highly porous materials, these sponges show extremely low densities (<3 mg cm(-3)) in combination with low specific surface areas. The resulting hierarchical pore structure of the sponges gives basis for soft and reversibly compressible materials and to hydrophobic behavior in combination with excellent uptake for hydrophobic liquids. Owing to their large porosity, cell culturing is successful after hydrophilic modification of the sponges.

151) Thermoresponsive Gold Nanoparticles with Positive UCST-Type Thermoresponsivity.

Author(s): Liu, FY (Liu, Fangyao); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 216  Issue: 4  Pages: 460-465  DOI: 10.1002/macp.201400497  Published: FEB 2015  
Abstract: Trithiocarbonate end-functionalized poly(N-acryloylglycinamide) (PNAGA), synthesized via reversible addition-fragmentation transfer (RAFT) polymerization of different molecular weights, is grafted onto gold nanoparticles (AuNPs) by ligand exchange in phosphate-buffered saline. The PNAGA-grafted AuNPs display upper critical solution temperature (UCST)-type transitions: stable colloidal distribution and aggregation above and below the cloud points, respectively. Cloud points of PNAGA are not affected by the grafting procedure, and PNAGA@AuNPs show similar cloud points as that of the trithiocarbonate end-functionalized free-PNAGAs used for grafting. The UCST-type phase transition is reversible for many cycles. The reversible control of the phase transition is proved by turbidity measurements and UV-vis spectroscopy, as well as by transmission electron microscopy (TEM).

150) Preparing a Pseudo-solid by the Reinforcement of a Polydentate Thioether using Silver Nanoparticles.

Author(s): Pletsch, H (Pletsch, Holger); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: NANOSCALE  Volume: 7  Issue: 5  Pages: 1977-1983  DOI: 10.1039/c4nr06834c  Published: 2015  
Abstract: The design of networks from polymers and noble metal nanoparticles requires thorough control over topological polymer-particle arrangements. This study explores the interaction between a linear polydentate poly(propylene sulfide) (PPrS) ligand and silver nanoparticles (AgNPs) with an aim to study its effect on mechanical and viscoelastic properties. Very low amounts (0.30 vol%) of silver nanoparticles lead to significant mechanical reinforcement of PPrS, yielding viscoelastic properties of an unfastened network with solid-like elastic responses on mechanical stimulation. The materials are made by ring-opening anionic polymerization of propylene sulfide to yield high molar mass PPrS with a total of 593 thioether functionalities per chain, followed by a simple in situ "grafting to" method to homogeneously incorporate AgNPs into the polymer matrix. From investigations on the chain dynamics using dynamic rheology it is concluded that well-dispersed AgNPs impose additional topological constraints on the polymer chains. Calculations of the statistical interparticle distances support a tele-bridging polymer-particle arrangement.

149) Low volume shrinkage of polymers by photopolymerization of 1,1-bis(ethoxycarbonyl)-2-vinylcyclopropanes.

Author(s): Contreras, PP (Contreras, Paul Pineda); Tyagi, P (Tyagi, Payal); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 6  Issue: 12  Pages: 2297-2304  DOI: 10.1039/c4py01705f  Published: 2015  
Abstract: Low volume shrinkage of polymers by photoring-opening polymerization of 1,1-bis(ethoxycarbonyl)-2-vinylcyclopropane (VCP) and its methyl substituted derivate 1,1-bis(ethoxycarbonyl)-2-(prop-1-en-2-yl)cyclopropane (Me-VCP) is presented. The aim of this study was to evaluate the photopolymerization behavior and structure of the corresponding polymers from VCP and its methyl substituted derivates 1,1-bis(ethoxycarbonyl)-2-(prop-1-en-2-yl)-cyclopropane (Me-VCP) and 1,1-bis(ethoxycarbonyl)-2-methyl-2-(prop-1-en-2-yl)-cyclopropane (DiMeVCP). VCP monomers were polymerized using camphorquinone (CQ) as a photo-initiator either in a binary or ternary photo-initiator system. The binary systems were formulated with ethyl 4-dimethylaminobenzoate (EDMAB) in relation to the monomer and 1 mol% of CQ. The ternary system was a mixture of 1 mol% of CQ, 2 mol% of EDMAB and 2 mol% of DPIHFP. Ternary photo-initiator systems showed high polymerization rates leading to high conversion in a short photoactivation time. One of the important findings is the formation of higher amounts of 1,5-type ring-opened units and lower amounts of cyclobutane-containing units in photopolymerization, which can make VCP an attractive component of dental composites, as the volume shrinkage is proportional to the 1,5-ring opening. Earlier it was observed that thermal free radical polymerization of VCPs gives higher amounts of cyclobutane structures compared to 1,5-type ring-opened units in the corresponding polymers, causing VCP to be excluded from the list of promising dental composites, as the volume shrinkage was higher than expected.

148) Thermophilic films and fibers from photo cross-linkable UCST-type polymers.

Author(s): Liu, FY (Liu, Fangyao); Jiang, SH (Jiang, Shaohua); Ionov, L (Ionov, Leonid); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 6  Issue: 14  Pages: 2769-2776  DOI: 10.1039/c5py00109a  Published: 2015  
Abstract: Photo cross-linkable thermoresponsive polymers of UCST-type based on acrylamide (AAm) and acrylonitrile (AN) useful for preparing thermophilic hydrogel films and fibers are presented. The polymers prepared via free radical and reversible addition fragmentation chain-transfer (RAFT) polymerization methods using N-(4-benzoylphenyl) acrylamide (BPAm) as photo cross-linkable comonomers provided highly stable UCST-type phase transition in water reproducible without hysteresis for many cycles. The cloud point could be manipulated by varying the acrylonitrile amount in the feed. Chemically cross- linked hydrogel films and nanofibers (average diameter 500 nm) were successfully prepared from the ter-co-polymers by solution casting and electrospinning followed by UV irradiation. These hydrogels showed a continuous positive volume transition behavior in water with increasing temperature that was utilized for the design of microactuators.

147) Antibacterial 45S5 bioglass-based scaffolds reinforced with genipin cross-linked gelatin for bone tissue engineering.

Author(s): Li, W (Li, Wei); Wang, H (Wang, Hui); Ding, YP (Ding, Yaping); Scheithauer, EC (Scheithauer, Ellen C.); Goudouri, OM (Goudouri, Ourania-Menti); Grunewald, A (Gruenewald, Alina); Detsch, R (Detsch, Rainer); Agarwal, S (Agarwal, Seema); Boccaccini, AR (Boccaccini, Aldo R.)
Source: JOURNAL OF MATERIALS CHEMISTRY B  Volume: 3  Issue: 16  Pages: 3367-3378  DOI: 10.1039/c5tb00044k  Published: 2015  
Abstract: 45S5 Bioglass (R) (BG) scaffolds with high porosity (>90%) were coated with genipin cross-linked gelatin (GCG) and further incorporated with poly(p-xylyleneguanidine) hydrochloride (PPXG). The obtained GCG coated scaffolds maintained the high porosity and well interconnected pore structure. A 26-fold higher compressive strength was provided to 45S5 BG scaffolds by GCG coating, which slightly retarded but did not inhibit the in vitro bioactivity of 45S5 BG scaffolds in SBF. Moreover, the scaffolds were made antibacterial against both Gram-positive and Gram-negative bacteria by using polyguanidine, i.e. PPXG, in this study. Osteoblast-like cells (MG-63) were seeded onto PPXG and GCG coated scaffolds. PPXG was biocompatible with MG-63 cells at a low concentration (10 mu g mL(-1)). MG-63 cells were shown to attach and spread on both uncoated and GCG coated scaffolds, and the mitochondrial activity measurement indicated that GCG coating had no negative influence on the cell proliferation behavior of MG-63 cells. The developed novel antibacterial bioactive 45S5 BG-based composite scaffolds with improved mechanical properties are promising candidates for bone tissue engineering.

146) Designed enzymatically degradable amphiphilic conetworks by radical ring-opening polymerization.

Author(s): Shi, YF (Shi, Yinfeng); Schmalz, H (Schmalz, Holger); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 6  Issue: 35  Pages: 6409-6415  DOI: 10.1039/c5py00962f  Published: 2015  
Abstract: A new route for the preparation of enzymatically degradable amphiphilic conetworks (APCNs) based on unsaturated polyesters by radical ring-opening copolymerization of vinylcyclopropane (VCP) with cyclic ketene acetal (CKA) is presented in this article. In the first step, the unsaturated biodegradable polyesters with random distribution of cross-linkable double bonds and degradable ester units were prepared by radical ring-opening copolymerization of VCP and CKA such as 2-methylene-4-phenyl-1,3-dioxolane (MPDO). Very similar reactivity ratios (r(VCP) = 0.23 +/- 0.08 and r(MPDO) = 0.18 +/- 0.02), unimodal gel permeation chromatography (GPC) curves and 2D NMR technique (heteronuclear multiple bond correlation, HMBC) showed the formation of random copolymers with unsaturation and ester units. The unsaturated units were used for cross-linking by radical polymerization with a hydrophilic macromonomer (oligo(ethylene glycol) methacrylate, OEGMA) in a second step for the formation of enzymatically degradable amphiphilic conetworks (APCNs). Enzymatic degradability was studied using Lipase from Pseudomonas cepacia. Due to the hydrophilic (HI) and hydrophobic (HO) microphase separation, the APCNs showed swelling in both water and organic solvents with different optical properties. The method provides an interesting route for making functional biodegradable APCNs using radical chemistry in the future by choosing appropriate vinyl comonomers.

145) Renaissance for low shrinking resins: all-in-one solution by bi-functional vinylcyclopropane-amides.

Author(s): Contreras, PP (Contreras, Paul Pineda); Kuttner, C (Kuttner, Christian); Fery, A (Fery, Andreas); Stahlschmidt, U (Stahlschmidt, Ullrich); Jerome, V (Jerome, Valerie); Freitag, R (Freitag, Ruth); Agarwal, S (Agarwal, Seema)
Source: CHEMICAL COMMUNICATIONS  Volume: 51  Issue: 59  Pages: 11899-11902  DOI: 10.1039/c5cc03901k  Published: 2015  
Abstract: A low volume shrinking vinylcyclopropane (VCP) monomer, showing both a high reactivity and a low viscosity, was obtained by applying a sterically hindered and isomeric spacer element, incorporating intermolecular amide hydrogen bonds. The resulting properties locate this VCP system in a pronounced range that so far no other efficient and radical polymerizable resin could enter.


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144) Solvent-free aqueous dispersions of block copolyesters for electrospinning of biodegradable nonwoven mats for biomedical applications.

Author(s): Bubel, K (Bubel, Kathrin); Grunenberg, D (Grunenberg, Daniel); Vasilyev, G (Vasilyev, Gleb); Zussman, E (Zussman, Eyal); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 299  Issue: 12  Pages: 1445-1454  DOI: 10.1002/mame.201400116  Published: DEC 2014  
Abstract: Biodegradable block copolyesters are processed from water to water-stable electrospun fibers without use of any organic solvent, which is of major importance for a variety of applications. The copolyesters (poly(epsilon-caprolactone-b-methoxypolyethylene glycol)) (PCL-b-MPEG)) are emulsified in water at 90 degrees C in presence of poly(ethylene oxide) (PEO) using melt dispersion method. Dramatic increase in viscosity is observed upon addition of PEO to aqueous dispersions of copolyesters. Evidence of structure formation in aqueous PCL-b-MPEG/PEO dispersions is adduced using rheological studies. PCL block length dependent water stable nanofiber non-wovens are obtained upon electrospinning of the dispersions.

143) Template Assisted Change in Morphology from Particles to Nanofibers by Side-by-Side Electrospinning of Block Copolymers. 

Author(s): Jiang, SH (Jiang, Shaohua); Jin, Q (Jin, Qiao); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 299  Issue: 11  Pages: 1298-1305  DOI: 10.1002/mame.201400059  Published: NOV 2014  
Abstract: Template assisted change in morphology from particles to nanofibers was shown for low molar mass amphiphilic block copolymers by side-by-side electrospinning. The reversibly cross-linkable particles and fibers could be easily obtained from the same polymeric material by choosing proper processing conditions and spinning nozzles. The conventional electrospinning with single-component nozzle provided only particles. The morphology of the particles was controlled by varying the electrospraying conditions and characterized by SEM, optical microscope, and AFM. The same low molecular weight non-spinnable polymers provided fibrous morphology by Template Assisted Method (TAM) using side-by-side electrospinning nozzle with PEO as sacrificial polymer.<inline-graphic xmlns:xlink="" xlink:href="">mame201400059-gra-0001</inline-graphic

142) One step preparation of reduction-responsive biodegradable polymers as efficient intracellular drug delivery platforms.

Author(s): Cai, TJ (Cai, Tongjiang); Chen, YJ (Chen, Yangjun); Wang, Y (Wang, Yin); Wang, HB (Wang, Haibo); Liu, XS (Liu, Xiangsheng); Jin, Q (Jin, Qiao); Agarwal, S (Agarwal, Seema); Ji, J (Ji, Jian)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 215  Issue: 19  Pages: 1848-1854  DOI: 10.1002/macp.201400311  Published: OCT 2014  
Abstract: Reduction-responsive biodegradable polymeric micelles based on functional 2-methylene-1,3-dioxepane (MDO) copolymers are developed and investigated for triggered doxorubicin (DOX) release. The MDO-based copolymers P(MDO-co-PEGMA-co-PDSMA) are synthesized via the simple one-step radical ring-opening copolymerization of MDO, poly(ethylene glycol) methyl ether methacrylate (PEGMA), and pyridyldisulfide ethylmethacrylate (PDSMA). The copolymers can self-assemble to form micelles in aqueous solution. DOX, a model anticancer drug, is loaded into the micelles with the drug loading content (DLC) of 11.3%. The micelles can be disassembled under a reductive environment (10 x 10(-3)m glutathione), which results in a triggered drug release behavior. The glutathione-mediated intracellular drug release of DOX-loaded micelles is investigated against A549 cells. Confocal laser scanning microscopy (CLSM) results demonstrated that DOX-loaded micelles exhibits faster drug release in glutathione monoester (GSH-OEt)-pretreated A549 cells, compared with untreated and buthionine sulfoximine (BSO)-pretreated A549 cells. Based on the facile synthetic strategy, the reduction-sensitive biodegradable micelles with triggered intracellular drug release are promising for anticancer drug delivery.

141) Design of Soft Materials from Liquid Triblock Co-Oligomers and Metal Nanoparticles.

Author(s): Pletsch, H (Pletsch, Holger); Schnepf, MJ (Schnepf, Max J.); Agarwal, S (Agarwal, Seema)
Source: CHEMISTRY OF MATERIALS  Volume: 26  Issue: 16  Pages: 4805-4811  DOI: 10.1021/cm502322g  Published: AUG 26 2014  
Abstract: Thermally processable soft material networks with adjustable mechanical properties made from very low molar mass alpha,omega-dithiol functionalized ABA triblock co-oligomers (alpha,omega-dithiol oligo(isoprene-b-styrene-b-isoprene) (TISIT)) using AgNP as thermally reversible cross-linking points are highlighted in the present work. Liquid TISIT oligomers were synthesized by sequential anionic polymerization and subsequently cross-linked with AgNP. Low molar masses (4200-4800 g mol(-1)) were engaged, assuring disordered microstructures and therefore, low viscosities at elevated temperatures. Smooth films with homogeneous nanoparticle distributions of the resulting quasi-segmented soft material networks (TISIT@AgNP) were made by heat pressing. The interplay of styrene and AgNP as the structure-supplying portions in TISIT@AgNP samples facilitates access to materials with tensile strengths up to 5.58 MPa, toughness up to 13.3 MN mm(-2), and tensile moduli up to 80.1 MPa at room temperature and strongly decreased elasticity and viscosity at elevated temperatures, even below the glass transition temperature of polystyrene.

140) A non-ionic thermophilic hydrogel with positive thermosensivity in water and electrolyte solution.

Author(s): Liu, FY (Liu, Fangyao); Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 215  Issue: 15  Pages: 1466-1472  DOI: 10.1002/macp.201400155  Published: AUG 2014  
Abstract: The first example of a chemically crosslinked synthetic non-ionic hydrogel showing reversible positive swelling behavior in pure water as well as electrolyte solution is highlighted. Homopolymeric hydrogels are synthesized from N-acryloylglycinamide with N,N-methylenbis(acrylamide) as a chemical crosslinker via free radical polymerization in dimethyl sulfoxide (DMSO). The swelling-ratio dependency of the hydrogels upon temperature as well as on the amounts of crosslinker from 1 to 4.8 mol% is studied. With 1 mol% crosslinker, the hydrogel is able to take up over three times water of its weight at 37 degrees C in pure water and phosphate-buffered saline. All the samples show almost 100% of reversibility for at least 6 d up to 37 degrees C irrespective of the amount of the crosslinker, making them promising candidates for biomedical applications. The sample with a higher amount of crosslinker, i.e., 4.8 mol% is even stable for over 6 d at 70 degrees C.

139) Oligomeric dual functional antibacterial polycaprolactone.

Author(s): Wang, H (Wang, Hui); Synatschke, CV (Synatschke, Christopher V.); Raup, A (Raup, Alexander); Jerome, V (Jerome, Valerie); Freitag, R (Freitag, Ruth); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 5  Issue: 7  Pages: 2453-2460  DOI: 10.1039/c3py01467c  Published: 2014  
Abstract: Dual functional antibacterial and biodegradable caprolactone (CL) based oligomers were prepared by ring-opening polymerization of caprolactone using a polyguanidine macroinitiator. Primary amino (-NH2) end-groups of linear poly(hexamethylene guanidine) hydrochloride (PHMG) acted as initiating sites for caprolactone polymerization leading to block copolymers which combine the antibacterial properties of PHMG with degradability provided by PCL. The block structure of the material was confirmed with 2D NMR and MALDI-ToF-MS. Furthermore, the material exhibited temperature dependent solubility (upper critical solution temperature) in polar solvents such as methanol. The oligomers showed high antibacterial activity (reduction of bacterial cells was more than 3 orders of magnitude) even at short incubation times depending on the concentration and PHMG : PCL ratio while maintaining enzymatic degradability and biocompatibility.

138) Importance of compositional homogeneity of macromolecular chains for UCST-type transitions in water: Controlled versus conventional radical polymerization.

Source: JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY  Volume: 52  Issue: 13  Pages: 1878-1884  DOI: 10.1002/pola.27196  Published: JUL 1 2014  
Abstract: The change of polymerization method from conventional free radical polymerization to the reversible addition fragmentation chain transfer (RAFT) method provided thermoresponsive behavior of upper critical solution temperature (UCST)-type in water to copolymers of styrene (St) and acrylamide (AAm). Sample preparation conditions (temperature and time of dissolution) for turbidity measurements could also significantly influence the thermoresponsive behavior of polymers based on AAm. Poly(AAm-co-St)s made by RAFT method till high conversions showed sharp cloud points ranging 50-62 degrees C with low hysteresis in water depending upon the copolymer composition. Samples for turbidity measurements were prepared under optimized conditions, that is, 70 degrees C for 1.5 h. In contrast, the copolymers made by conventional radical polymerization in all copolymer composition range were not thermoresponsive. The example [poly(AAm-co-St)] emphasizes the importance of compositional homogeneity of macromolecular chains for showing UCST-type transitions in water for a system with wide difference in reactivity ratios of the comonomers. Since, examples of polymeric systems showing UCST in water are not too many, this work highlights how compositional homogeneity would help in developing many more systems with tuned cloud points. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1878-1884

137) A rare example of the formation of polystyrene-grafted aliphatic polyester in one-pot by radical polymerization.

Author(s): Shi, YF (Shi, Yinfeng); Zheng, ZC (Zheng, Zhicheng); Agarwal, S (Agarwal, Seema)
Source: CHEMISTRY-A EUROPEAN JOURNAL  Volume: 20  Issue: 24  Pages: 7419-7428  DOI: 10.1002/chem.201400238  Published: JUN 10 2014  
Abstract: The radical copolymerization of cyclic ester beta-propiolactone (beta-PL) with styrene (St) at 120 degrees C, with a complete range of monomer ratios, is a rare example of a system providing graft copolymers (PSt-g-beta-PL) in one pot. The structure of the resulting beta-PL-St copolymers was proven by using a combination of different characterization techniques, such as 1D and 2D NMR spectroscopy and gel permeation chromatography (GPC), before and after alkaline hydrolysis of the polymers. The number of grafting points increased with an increasing amount of beta-PL in the feed. A significant difference in the reactivity of St and beta-PL and radical chain-transfer reactions at the polystyrene (PSt) backbone, followed by combination with the active growing poly(beta-PL) chains, led to the formation of graft copolymers by a grafting-onto mechanism.

136) Tea-bag-like polymer nanoreactors filled with gold nanoparticles.

Author(s): Mitschang, F (Mitschang, Fabian); Schmalz, H (Schmalz, Holger); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION  Volume: 53  Issue: 19  Pages: 4972-4975  DOI: 10.1002/anie.201402212  Published: MAY 5 2014  
Abstract: Gold-containing polymer nanotubes, which showed both catalytic activity and resistance to leaching, were prepared by the tubes by fiber templates (TUFT) process. For this purpose, electrospun polymer nonwovens with incorporated poly(L-lactide)-stabilized gold nanoparticles were coated with poly(p-xylylene) by the chemical vapor deposition process, and then the inner fiber templates were removed. The resulting polymer tubes carried encapsulated gold nanoparticles which were shown to be immobilized and featured pronounced catalytic activity towards the hydrolytic oxidation of dimethylphenylsilane and the alcoholysis of dimethylphenylsilane with n-butanol. The macroscopic nonwovens could be used as tea-bag-like catalyst systems and showed excellent reusability.

135) Highly flexible and tough concentric triaxial polystyrene fibers.

Author(s): Jiang, SH (Jiang, Shaohua); Duan, GG (Duan, Gaigai); Zussman, E (Zussman, Eyal); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: ACS APPLIED MATERIALS & INTERFACES  Volume: 6  Issue: 8  Pages: 5918-5923  DOI: 10.1021/am500837s  Published: APR 23 2014  
Abstract: A combination of appropriate reinforcing material and morphology led to the highly tough, flexible, and strong polystyrene fibers by electrospinning. Concentric fiber morphology with reinforcing elastomeric thermoplastic polyurethane (TPU) sandwiched between the two layers of polystyrene made by a special nozzle (triaxial) showed toughness of >270 J g(-1) and 300% elongation without any cracks in comparison to toughness of <0.5 J g(-1) and elongation at break of <5% of polystyrene single fibers. The concentric triaxial morphology showed great advantage in comparison to the coaxial structure. Toughness and elongation at break were 1376 and 628% higher, respectively, for triaxial morphology in comparison to the from the sandwich structure.

134) Blocked bacteria escape by ATRP grafting of a PMMA shell on PVA microparticles.

Author(s): Knierim, C (Knierim, Christian); Greenblatt, CL (Greenblatt, Charles L.); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 14  Issue: 4  Pages: 537-545  DOI: 10.1002/mabi.201300398  Published: APR 2014  
Abstract: This paper reports on the preparation and characterization of living composites consisting of poly(vinylalcohol) (PVA) hydrogel microparticles with living bacteria and a shell of poly(methyl methacrylate) (PMMA). The grafting of the PMMA shell is accomplished in the presence of living bacteria by surface polymerization of PMMA using atom transfer radical polymerization (ATRP). The PMMA shell prevents the uncontrolled bacterial escape from the hydrogel microparticles, which otherwise marks a major problem of these composites. The encapsulation of microparticles with living bacteria by PMMA retards bacteria escape upon contact to water for >20 d. The functionality of the PMMA shell is proven both by the release of fluorescein in buffer and an altered release time of bacteria in buffer solution.

133) Ultrasound- mediated synthesis of high-molecular weight polystyrene-grafted silver nanoparticles by facile ligand exchange reactions in suspension.

Author(s): Pletsch, H (Pletsch, Holger); Peng, L (Peng, Ling); Mitschang, F (Mitschang, Fabian); Schaper, A (Schaper, Andreas); Hellwig, M (Hellwig, Michael); Nette, D (Nette, David); Seubert, A (Seubert, Andreas); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: SMALL  Volume: 10  Issue: 1  Pages: 201-208  DOI: 10.1002/smll.201300594  Published: JAN 15 2014  
Abstract: Ultrasound mediated facile ligand exchange method in suspension for the formation of polystyrenegrafted silver nanoparticles is reported. Amazingly, this method allows even grafting of very high molecular weight polystyrenes (up to 217 200 g mol(-1)) having a single terminal thiol group at the chain end. Detailed studies are carried out to gain insights in the role of molecular weight of the ligands and the mechanism of the ligand exchange reactions. Key factors are determined to be the droplet formation by ultrasonification and low silver content, which enhances the availability of the terminal thiol end group significantly. The extraordinary compatibility of the ligand exchange method in particular regarding high molecular weights is attributed to hydrophilic orientation of the terminal thiol groups at the liquidliquid interphase. This is proved conclusively by using an in situ method as a reference approach in which agglomeration occurs at considerably lower molecular weights due to the absence of preferred end group orientation within the polymer coil. In homogeneous phase only the chain length is found to be the crucial factor in stabilization of silver nanoparticles.

132) Functional 2-methylene-1,3-dioxepane terpolymer: a versatile platform to construct biodegradable polymeric prodrugs for intracellular drug delivery.

Author(s): Cai, TJ (Cai, Tongjiang); Chen, YJ (Chen, Yangjun); Wang, Y (Wang, Yin); Wang, HB (Wang, Haibo); Liu, XS (Liu, Xiangsheng); Jin, Q (Jin, Qiao); Agarwal, S (Agarwal, Seema); Ji, J (Ji, Jian)
Source: POLYMER CHEMISTRY  Volume: 5  Issue: 13  Pages: 4061-4068  DOI: 10.1039/c4py00259h  Published: 2014  
Abstract: Functional 2-methylene-1,3-dioxepane (MDO) terpolymers were explored here as a versatile platform to construct biodegradable pH sensitive polymeric prodrugs for intracellular drug delivery. A series of MDO-based biodegradable functional polyester P(MDO-co-PEGMA-co-PDSMA) with different compositions were synthesized by terpolymerization of MDO, poly(ethylene glycol) methyl ether methacrylate (PEGMA) and pyridyldisulfide ethylmethacrylate (PDSMA) via a simple one-pot radical ring-opening copolymerization. Mal-DOX, which contains a pH-sensitive hydrazone bond between doxorubicin (DOX) and the maleimide group, was covalently conjugated in one pot to free thiol groups of PDSMA units via thiol-ene click chemistry in the presence of tri(2-carboxyethyl) phosphine (TCEP). The DOX-conjugated P(MDO-co-PEGMA-co-PDSMA) can self-assemble into prodrug micelles. The diameter and morphology of the polymeric prodrug micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Because of the existence of the pH-sensitive hydrazone bonds, in vitro drug release results showed that the release of DOX was much faster at pH 5.5 than that at pH 7.4. Flow cytometry and fluorescence microscopy demonstrated that the prodrug micelles could be efficiently internalized by cancer cells. In vitro cytotoxicity showed that the DOX-conjugated prodrug micelles can strongly inhibit the proliferation of cancer cells remarkably. Importantly, this work provides a versatile strategy for the fabrication of biodegradable polymeric prodrug nanocarriers.


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131) Smart secondary polyurethane dispersions.

Author(s): Chen, F (Chen, Fei); Hehl, J (Hehl, Judith); Su, Y (Su, Yu); Mattheis, C (Mattheis, Claudia); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: POLYMER INTERNATIONAL  Volume: 62  Issue: 12  Pages: 1750-1757  DOI: 10.1002/pi.4481  Published: DEC 2013  
Abstract: Secondary dispersions of cationic segmented polyurethanes (PUs) with thermoresponsivity (upper critical solution temperature (UCST) in water), high solid contents and antibacterial properties are highlighted in this paper. PUs were prepared by polyaddition reactions and subsequent quaternization with methyl iodide. No additional stabilizers, organic solvents or special procedures were required to obtain stable aqueous dispersions containing up to 10wt% PU; in contrast, stable dispersions were straightforwardly accessed by a combination of UCST behavior and repulsive electrostatic forces among the positively charged segments, which meets the requirements of a green chemistry process. Particle size and UCST strongly depended on the solid content of the dispersions and the content of poly(ethylene glycol) segments in the copolymers. The dispersions exhibited fast-acting antibacterial properties against Escherichia coli. (c) 2013 Society of Chemical Industry

130) Short electrospun polymeric nanofibers reinforced polyimide nanocomposites. 

Author(s): Jiang, SH (Jiang, Shaohua); Duan, GG (Duan, Gaigai); Schobel, J (Schoebel, Judith); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: COMPOSITES SCIENCE AND TECHNOLOGY  Volume: 88  Pages: 57-61  DOI: 10.1016/j.compscitech.2013.08.031  Published: NOV 14 2013  
Abstract: This work highlights the usage of short electrospun fibers for the first time for the preparation of homogeneous polymer nanofiber/polymer composites and the improvement in mechanical properties by an order to magnitude compared to as-electrospun long and continuous nanofibers. Dispersions of short electrospun nanofibers can be processed by liquid processing techniques resulting in nanofiber nonwoyens similar to electrospun nonwovens but is independent from the demands of the electrospinning process is one of the emphasis of this work. The re-formation of electrospun fiber nonwovens by dispersion casting of short electrospun polyimide (PI) nanofibers and the preparation of homogeneous polymer/polymer nanofiber composite films were selected as representative examples for showing the versatility of short electrospun fibers. The self-reinforced PI/PI-short nanofiber composite films were obtained from mixtures of short electrospun PI nanofibers and polyamic acid after imidization. Significant improvement of 53% and 87% in mechanical properties like tensile strength and modulus, respectively in comparison to the neat PI film was observed by using just 2 wt% of short fibers. Parallel experiments were also carried out with long and continuous electrospun PI fibers and amazingly a huge difference was observed. The amount of continuously long fibers required for achieving almost the same strength was much higher i.e. 38 wt% in comparison to the 2 wt% required of short fibers. (C) 2013 Elsevier Ltd. All rights reserved.

129) Short nylon- 6 nanofiber reinforced transparent and high modulus thermoplastic polymeric composites.

Author(s): Jiang, S (Jiang, Shaohua); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: COMPOSITES SCIENCE AND TECHNOLOGY  Volume: 87  Pages: 164-169  DOI: 10.1016/j.compscitech.2013.08.011  Published: OCT 18 2013  
Abstract: The use of small amounts (<5 wt%) of short nylon-6 nanofibers (diameter less than 200 nm) for reinforcing mechanical properties of TPU without losing its optical properties is highlighted in this work. The interaction of H-bonding type between the reinforcing fibers and the matrix polymer could provide a homogenous distribution of fibers and a strong interface leading to significant enhancement in mechanical properties (185% increase in E modulus) as shown by comparative use of TPU and PMMA as matrix polymers. The reinforcing effect of short fibers was attained without sacrificing transparency (>90% transparency in 400-800 nm range) of TPU. The effective use of short nylon-6 fibers in comparison to the long and continuous fibers is also discussed. (C) 2013 Elsevier Ltd. All rights reserved.

128) Degradable and biocompatible poly(N, N- dimethylaminoethyl methacrylate- co- caprolactone) s as DNA transfection agents. 

Author(s): Zhang, Y (Zhang, Yi); Aigner, A (Aigner, Achim); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 13  Issue: 9  Pages: 1267-1275  DOI: 10.1002/mabi.201300043  Published: SEP 2013  
Abstract: This study describes the synthesis of a set of novel, degradable block copolymers for DNA transfection, and analyzes their physicochemical and biological properties. PEO macro-azoinitiators are used for the free radical copolymerization of DMAEMA and MDO, resulting in a series of different quaternized or non-quaternized block copolymers. All of the polymers show little cytotoxicity and full degradability, and thus, based on their favorable properties, may represent promising vectors for in vivo applications. Marked differences in DNA complexation efficacies and biological activities are observed, and one of the poly(PEG-co-(MDO-co-DMAEMA))s is identified as optimal for DNA transfection.

127) Tenside- free biodegradable polymer nanofiber nonwovens by "green electrospinning". 

Author(s): Bubel, K (Bubel, Kathrin); Zhang, Y (Zhang, Yi); Assem, Y (Assem, Yasser); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULES  Volume: 46  Issue: 17  Pages: 7034-7042  DOI: 10.1021/ma401044s  Published: SEP 10 2013  
Abstract: This work highlights the formation and use of tenside-free biodegradable polyester dispersions in water for making water stable nanofibers in accordance with the method of "Green Electrospinning". The concept was to use the amphiphilic block copolyesters poly[(hexamethylene adipate)-block-(methoxypolyethylene glycol)] (PHA-b-MPEG) and poly[(epsilon-caprolactone)-block-(methoxypolyethylene glycol)] (PCL-b-MPEG) for making tenside-free water dispersions. Different copolymers with varied block lengths were synthesized and converted to high-concentration aqueous dispersions by the solvent displacement method followed by dialysis. The dispersions were electrospun with solid contents of up to 28 wt %. Via addition of small amounts of a high-molecular weight poly(ethylene oxide) as a template polymer, the dispersions were processed to nanofiber nonwovens by electrospinning. Water stable PHA-b-MPEG and PCL-b-MPEG nanofibers were obtained by aqueous extraction of the nanofibers.

126) Polymers with upper critical solution temperature in aqueous solution: unexpected properties from known building blocks.

Author(s): Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema)
Source: ACS MACRO LETTERS  Volume: 2  Issue: 7  Pages: 597-600  DOI: 10.1021/mz400227y  Published: JUL 2013  
Abstract: Polymers showing an upper critical solution temperature (UCST) in aqueous solution were not rare, but the UCST was rarely observed under practically relevant conditions. Recently, much progress has been made in the synthesis of polymer systems that display UCST behavior under mild and physiologic conditions. Current developments focus on polymers that rely on hydrogen bonding. This viewpoint explains the historical context, presents the major properties, and concludes with a discussion of the most recent examples.

125) Chameleon nonwovens by green electrospinning. 

Author(s): Giebel, E (Giebel, Elisabeth); Mattheis, C (Mattheis, Claudia); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: ADVANCED FUNCTIONAL MATERIALS  Volume: 23  Issue: 25  Pages: 3156-3163  DOI: 10.1002/adfm.201201873  Published: JUL 5 2013  
Abstract: Electrospun ionic nonwovens are obtained by green electrospinning of aqueous dispersions. The resulting nonwovens are termed as chameleon nonwovens since their surface properties can be tailored in a large variety by coating of different functionalities following the protocol of the layer-by-layer process (LBL). The dimensional stability of the electrospun fibers in the chameleon nonwovens is achieved by photo-cross-linking after electrospinning and thereby overcoming the repulsive forces of the ionic moieties in the fibers. Depending on the nature of the ionic moieties different materials are coated by LBL including dyes, antibacterial materials, silver, and gold nanoparticles. Enhanced coating efficiency for coating of metal nanoparticles is observed when the chameleon nonwovens were precoated by a polyelectrolyte.

124) Exploring suitable oligoamines for phantom ring- closing condensation polymerization with guanidine hydrochloride. 

Author(s): Mattheis, C (Mattheis, Claudia); Wang, H (Wang, Hui); Schwarzer, MC (Schwarzer, Martin C.); Frenking, G (Frenking, Gernot); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 4  Issue: 3  Pages: 707-716  DOI: 10.1039/c2py20672b  Published: 2013  
Abstract: Different model compounds were applied in step-growth condensation reactions with guanidine hydrochloride in order to explore the scope of tri- and oligoamine applicability for phantom ring-closing condensation polymerization processes. The selective formation of five-membered rings was proven by APCI mass spectrometry, different one- and two-dimensional homo-and heteronuclear coupling NMR techniques and investigated via quantum chemical calculations. Furthermore the possibility of ring-closing reactions among guanidine hydrochloride and merely secondary amines was precluded. The obtained oligomers were exposed to antibacterial tests and exhibited a moderate activity towards Escherichia coli.

123) Functional materials by electrospinning of polymers. 

Author(s): Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas); Wendorff, JH (Wendorff, Joachim H.)
Source: PROGRESS IN POLYMER SCIENCE  Volume: 38  Issue: 6  Pages: 963-991  DOI: 10.1016/j.progpolymsci.2013.02.001  Published: JUN 2013  
Abstract: About a decade ago electrospinning was primarily concerned with the preparation of nanofibers from synthetic polymers and to a lower degree from natural polymers targeting predominantly technical applications areas such as textiles and filters as well as medical areas such as tissue engineering and drug delivery. Since then strong progress has been made not only in the understanding and theoretical modeling of the complex processes governing electrospinning and in the strict control of fiber formation by material and operating parameters but also in the design of a broad range of technical spinning devices. These achievements have in turn allowed for an extension of electrospinning towards fiber formation based not only on polymers of synthetic, biological nature but also on metals, metal oxides, ceramics, organic/organic, organic/inorganic as well as inorganic/inorganic composite systems. Here not only preparation schemes were investigated but properties and functions of the nanofibers were analyzed and potential applications were evaluated. As far as technical applications are concerned nanofibers composed of such materials can today be designed in a highly controlled way to display specific structural features. They include phase morphology and surface topology as well as unique functions including in particular magnetic, optical, electronic, sensoric, catalytic functions specific for one-dimensional architectures. Significant developments have also been achieved towards the exploitation of such functional nanofibers in applications involving among others fuel cells, lithium ion batteries, solar cell, electronic sensors as well as photocatalysts. One major target is currently the incorporation of such functional nanofibers in micrometer-sized electronic devices or even the construction of such devices purely from nanofibers. (C) 2013 Elsevier Ltd. All rights reserved.

122) Controlled antibody /(bio- ) conjugation of inorganic nanoparticles for targeted delivery.

Author(s): Montenegro, JM (Montenegro, Jose-Maria); Grazu, V (Grazu, Valeria); Sukhanova, A (Sukhanova, Alyona); Agarwal, S (Agarwal, Seema); de la Fuente, JM (de la Fuente, Jesus M.); Nabiev, I (Nabiev, Igor); Greiner, A (Greiner, Andreas); Parak, WJ (Parak, Wolfgang J.)
Source: ADVANCED DRUG DELIVERY REVIEWS  Volume: 65  Issue: 5  Pages: 677-688  DOI: 10.1016/j.addr.2012.12.003  Published: MAY 2013  
Abstract: Arguably targeting is one of the biggest problems for controlled drug delivery. In the case that drugs can be directed with high efficiency to the target tissue, side effects of medication are drastically reduced. Colloidal inorganic nanoparticles (NPs) have been proposed and described in the last 10 years as new platforms for in vivo delivery. However, though NPs can introduce plentiful functional properties (such as controlled destruction of tissue by local heating or local generation of free radicals), targeting remains an issue of intense research efforts. While passive targeting of NPs has been reported (the so-called enhanced permeation and retention, EPR effect), still improved active targeting would be highly desirable. One classical approach for active targeting is mediated by molecular recognition via capture molecules, i.e. antibodies (Abs) specific for the target. In order to apply this strategy for NPs, they need to be conjugated with Abs against specific biomarkers. Though many approaches have been reported in this direction, the controlled bioconjugation of NPs is still a challenge. In this article the strategies of controlled bioconjugation of NPs will be reviewed giving. particular emphasis to the following questions: 1) how can the number of capture molecules per NP be precisely adjusted, and 2) how can the Abs be attached to NP surfaces in an oriented way. Solution of both questions is a cornerstone in controlled targeting of the inorganic NPs bioconjugates. (C) 2013 Elsevier B.V. All rights reserved.

121) Atom transfer radical polymerization as a tool for making poly(N- acryloylglycinamide) with molar mass independent UCST- type transitions in water and electrolytes.

Author(s): Liu, FY (Liu, Fangyao); Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 4  Issue: 10  Pages: 3123-3131  DOI: 10.1039/c3py00222e  Published: 2013  
Abstract: Atom transfer radical polymerization (ATRP) of N-acryloylglycinamide has been used as a tool to make poly(NAGA) showing UCST-type phase transitions in water and electrolytes independent of molar mass and end-groups. We hypothesized that similarity in the structure of polymer chain ends with the repeat unit of poly(NAGA) could help in eliminating the effect of molar mass dependence of the cloud point especially in the low molar mass region. The monomer-like end-groups were introduced by choosing an appropriate initiator for ATRP like chloropropionamide (CPA). The catalyst system CuCl/CuCl2 and tris-[2-(dimethylamino)ethyl]-amine (Me6TREN) as a ligand provided controlled polymerization of NAGA in DMSO at 45 degrees C with UCST-type transitions retained in water and electrolytes without being influenced by chain ends/molar mass and high concentration of salts like NaCl and Na2SO4.

120) Effect of guanidinylation on the properties of poly(2- aminoethylmethacrylate) - based antibacterial materials.

Author(s): Mattheis, C (Mattheis, Claudia); Wang, H (Wang, Hui); Meister, C (Meister, Claus); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 13  Issue: 2  Pages: 242-255  DOI: 10.1002/mabi.201200217  Published: FEB 2013  
Abstract: The effect of converting ammonium into guanidine moieties, compared to other factors such as molecular weight or hydrophobicity, on the antibacterial activity is investigated for homo- and copolymers of 2-aminoethylmethacrylate in solution or coatings. Polymers are obtained by free radical polymerization, polymer-analogous guanidinylation is conducted with cyanamide; non-leaching immobilization is achieved by LBL assembly of homopolymers or crosslinking of functional sidegroups in copolymers. Antibacterial activity to Escherichia coli or Bacillus subtilis is determined by different standard methods. Guanidinylation improves antibacterial activity and speed as well as cytotoxicity of hydrophilic homo- and copolymers in solution or coatings.


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119) Controlled radical polymerization of N-acryloylglycinamide and UCST-type phase transition of the polymers. 

Title: Controlled Radical Polymerization of N-Acryloylglycinamide and UCST-Type Phase Transition of the Polymers
Author(s): Liu, FY (Liu, Fangyao); Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema)
Source: JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY  Volume: 50  Issue: 23  Pages: 4920-4928  DOI: 10.1002/pola.26322  Published: DEC 1 2012  
Abstract: N-Acryloylglycinamide was polymerized via the reversible addition fragmentation transfer process without sacrificing its key property, the upper critical solution temperature in water. This could be achieved by choosing an appropriate nonionic initiator [2,2'-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V-70)] and nonionic chain-transfer agent (cyanomethyl dodecyl trithiocarbonate). A good molar mass control was accomplished as proved by the linear increase of molar mass with conversion, a chain extension experiment, and low dispersity. The influence of molar mass, polymer end groups, or salt concentration on the cloud point was analyzed by turbidimetry. Polymer end groups exerted a distinct effect on the cloud points, whereas the influence increased with decreasing molar masses. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 4920-4928, 2012

118) Antimicrobial hydantoin- grafted poly(ε- caprolactone) by ring- opening polymerization and click chemistry. 

Author(s): Tan, LC (Tan, Licheng); Maji, S (Maji, Samarendra); Mattheis, C (Mattheis, Claudia); Chen, YW (Chen, Yiwang); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 12  Issue: 12  Pages: 1721-1730  DOI: 10.1002/mabi.201200238  Published: DEC 2012  
Abstract: Novel degradable and antibacterial polycaprolactone-based polymers are reported in this work. The polyesters with pendent propargyl groups are successfully prepared by ring-opening polymerization and subsequently used to graft antibacterial hydantoin moieties via click chemistry by a copper(I)-catalyzed azide-alkyne cycloaddition reaction. The well-controlled chemical structures of the grafted copolymers and its precursors are verified by FT-IR spectroscopy, NMR spectroscopy, and GPC characterizations. According to the DSC and XRD results, the polymorphisms of these grafted copolymers are mostly changed from semicrystalline to amorphous depending on the amount of grafted hydantoin. Antibacterial assays are carried out with Bacillus subtilis and two strains of Escherichia coli and show fast antibacterial action.

117) Polymers with upper critical solution temperature in aqueous solution.

Author(s): Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 33  Issue: 22  Pages: 1898-1920  DOI: 10.1002/marc.201200433  Published: NOV 23 2012  
Abstract: This review focuses on polymers with upper critical solution temperature (UCST) in water or electrolyte solution and provides a detailed survey of the yet few existing examples. A guide for synthetic chemists for the design of novel UCST polymers is presented and possible handles to tune the phase transition temperature, sharpness of transition, hysteresis, and effectiveness of phase separation are discussed. This review tries to answer the question why polymers with UCST remained largely underrepresented in academic as well as applied research and what requirements have to be fulfilled to make these polymers suitable for the development of smart materials with a positive thermoresponse.

116) Thermo-switchable antibacterial activity. 

Author(s): Mattheis, C (Mattheis, Claudia); Zhang, Y (Zhang, Yi); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 12  Issue: 10  Pages: 1401-1412  DOI: 10.1002/mabi.201200207  Published: OCT 2012  
Abstract: A copolymer system of 2-aminoethyl methacrylate and N-isopropylacrylamide comprises novel properties: changes in conformation and hydrophilicity upon heating influence the antibacterial activity and result in a switchable biocidal effect. The copolymers are characterized via NMR, MALDI-ToF MS, phase transition behavior, and antibacterial tests with E. coli or B. subtilis. MIC and MBC are determined using standard dilution methods, temperature-dependence via incubation at different temperatures and cytotoxicity by MTT tests. The copolymers exhibit lower MIC in globule than coil conformation, crosslinking on cotton results in non-leaching materials with better antibacterial activity above than below the phase-transition point.

115) PDMAEMA based gene delivery materials. 

Author(s): Agarwal, S (Agarwal, Seema); Zhang, Y (Zhang, Yi); Maji, S (Maji, Samarendra); Greiner, A (Greiner, Andreas)
Source: MATERIALS TODAY  Volume: 15  Issue: 9  Pages: 388-393  Published: SEP 2012  
Abstract: Gene transfection is the transfer of genetic material like DNA into cells. Cationic polymers which form nanocomplexes with DNA, so-called non-viral gene vectors, are a highly promising platform for efficient gene transfection. Despite intensive research efforts and some of the on-going clinical trials on gene transfection, none of the existing cationic polymer systems are generally acceptable for human gene therapy. Since the process of gene transfection is complex and puts different challenges and demands on the delivery system, there is a strong requirement for the design and development of a multifunctional system in a simple way. This review will discuss recent efforts in design, synthesis, and performance of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) nanocomplexes with DNA.

114) Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on colonization and bone formation in vivo.

Author(s): Schofer, MD (Schofer, Markus D.); Tunnermann, L (Tuennermann, Lisa); Kaiser, H (Kaiser, Hendric); Roessler, PP (Roessler, Philip P.); Theisen, C (Theisen, Christina); Heverhagen, JT (Heverhagen, Johannes T.); Hering, J (Hering, Jacqueline); Voelker, M (Voelker, Maximilian); Agarwal, S (Agarwal, Seema); Efe, T (Efe, Turgay); Fuchs-Winkelmann, S (Fuchs-Winkelmann, Susanne); Paletta, JRJ (Paletta, Juergen R. J.)
Source: JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE  Volume: 23  Issue: 9  Pages: 2227-2233  DOI: 10.1007/s10856-012-4697-0  Published: SEP 2012  
Abstract: The reconstruction of large bone defects after injury or tumor resection often requires the use of bone substitution. Artificial scaffolds based on synthetic biomaterials can overcome disadvantages of autologous bone grafts, like limited availability and donor side morbidity. Among them, scaffolds based on nanofibers offer great advantages. They mimic the extracellular matrix, can be used as a carrier for growth factors and allow the differentiation of human mesenchymal stem cells. Differentiation is triggered by a series of signaling processes, including integrin and bone morphogenetic protein (BMP), which act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffolds in vivo. Electrospun matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were implanted in calvarial critical size defects in rats. Cranial CT-scans were taken 4, 8 and 12 weeks after implantation. Specimens obtained after euthanasia were processed for histology and immunostainings on osteocalcin, BMP-2 and Smad5. After implantation the scaffolds were inhomogeneously colonized and cells were only present in wrinkle- or channel-like structures. Ossification was detected only in focal areas of the scaffold. This was independent of whether BMP-2 was incorporated in the scaffold. However, cells that migrated into the scaffold showed an increased ratio of osteocalcin and Smad5 positive cells compared to empty defects. Furthermore, in case of BMP-2 incorporated PLLA-collagen type I scaffolds, 4 weeks after implantation approximately 40 % of the cells stained positive for BMP-2 indicating an autocrine process of the ingrown cells. These findings indicate that a cooperative effect between BMP-2 and collagen type I can be transferred to PLLA nanofibers and furthermore, that this effect is active in vivo. However, this had no effect on bone formation. The reason for this seems to be an unbalanced colonization of the scaffolds with cells, due to insufficient pore size.

113) Ultra- long palladium nanoworms by polymer grafts.

Author(s): Bokern, S (Bokern, Stefan); Volz, K (Volz, Kerstin); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: JOURNAL OF NANOPARTICLE RESEARCH  Volume: 14  Issue: 8  Article Number: 1041  DOI: 10.1007/s11051-012-1041-z  Published: AUG 2012  
Abstract: Chemically and morphologically stable, non-aggregating palladium nanoworms with diameters of 2 nm and lengths of up to 10 nm with a graft-to polystyrene shell were synthesized in a straight-forward one-phase system, and proof for the mechanism of formation is presented. The synthesis has been achieved by the application of omega-2,2'-bipyridyl-polystyrene as stabilizer, which led to a "graft-to'' structure of palladium nanoworms with polystyrene shell. The nanoworms have been characterized by TEM, XRD, and coupled GPC-UV/Vis measurement. It was possible to show that the formation of nanoworms proceeds by agglomeration of spherical palladium nanoparticles. This mechanism was transferred to omega-thiol-polystyrene as stabilizer, which results in either spherical nanoparticles (low ratio Pd:Polymer, <2 nm diameter) or high aspect ratio nanoworms (high ratio Pd: Polymer, up to 10 x 120 nm), proving that the formation of palladium nanoworms was not exclusive for pyridine/amine-based ligands.

112) Novel amphiphilic, biodegradable, biocompatible, cross- linkable copolymers: synthesis, characterization and drug delivery applications.

Author(s): Jin, Q (Jin, Qiao); Maji, S (Maji, Samarendra); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 3  Issue: 10  Pages: 2785-2793  DOI: 10.1039/c2py20364b  Published: 2012  
Abstract: The synthesis of a new kind of amphiphilic poly(vinyl-co-ester)s via simple one-pot radical ring-opening polymerization (RROP) is reported. A series of biodegradable, biocompatible, and cross-linkable copolymers P(MDO-co-PEGMA-co-CMA) with different compositions were synthesized by copolymerization of 2-methylene-1,3-dioxepane (MDO), poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 7-(2-methacryloyloxyethoxy)-4-methylcoumarin methacrylate (CMA). All the copolymers were well characterized by H-1 NMR, C-13 NMR, and gel permeation chromatography (GPC). The hydrolytic degradation and enzymatic degradation of the copolymers were investigated. The amphiphilic P(MDO-co-PEGMA-co-CMA) can self-assemble into micelles in aqueous solution. Polymeric micelles with different sizes were obtained through tuning the compositions of the copolymers, i.e., the hydrophilic/hydrophobic ratio. The size and morphology of the micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Because of the coumarin side groups in the micellar core, the micelles can be cross-linked upon exposure to long-wavelength UV light (lambda = 365 nm). These micelles also showed excellent biocompatibility by the in vitro cytotoxicity experiments. Furthermore, the biodegradable micelles were applied for the delivery of an anticancer drug doxorubicin (DOX). The cell viability of DOX-loading micelles compared to free DOX was discussed. The effects of cross-linking and the copolymer composition on the drug release behavior were well studied. The results indicate that this new kind of amphiphilic poly(vinyl-co-ester) s could serve as promising nanocarriers for the delivery of anticancer drugs.

111) Biocompatible and degradable poly(2- hydroxyethyl methacrylate) based polymers for biomedical applications.

Title: Biocompatible and degradable poly(2-hydroxyethyl methacrylate) based polymers for biomedical applications
Author(s): Zhang, Y (Zhang, Yi); Chu, DF (Chu, Dafeng); Zheng, MY (Zheng, Mengyao); Kissel, T (Kissel, Thomas); Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 3  Issue: 10  Pages: 2752-2759  DOI: 10.1039/c2py20403g  Published: 2012  
Abstract: The present work provides a new, well characterized hydroxyl functionalized biocompatible and degradable polymer that could be suitable for many different biomedical applications. Poly(2-hydroxyethyl methacrylate) (PHEMA) is a widely used and researched biocompatible polymer, but lacks degradability. In this work, degradable and less toxic PHEMA with ester linkages in the backbone could be successfully made by radical copolymerization with cyclic ketene acetal. The protection-deprotection chemistry at the hydroxyl group of HEMA was necessary for the formation of targeted polymers. The structure of the resulting polymers was unambiguously proved by 2D NMR techniques. The polymers were significantly less toxic with cell viabilities of more than 80% even for very high polymer concentrations (100 mg mL(-1)). The polymers were hydrolytically degradable under basic conditions and also showed surface and bulk degradation using macrophages. We also demonstrated promising positive results for the use of such polymers as sustained drug delivery systems.

110) A fast degrading odd-odd aliphatic polyester-5,7 made by condensation polymerization for biomedical applications. 

Author(s): Chen, F (Chen, Fei); Nolle, JM (Noelle, Jan Martin); Wietzke, S (Wietzke, Steffen); Reuter, M (Reuter, Marco); Chatterjee, S (Chatterjee, Sangam); Koch, M (Koch, Martin); Agarwal, S (Agarwal, Seema)
Source: JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION  Volume: 23  Issue: 12  Pages: 1539-1551  DOI: 10.1163/092050611X585837  Published: 2012  
Abstract: A fast enzymatic degradable aliphatic all-odd-polyester-5,7, based on 1,7-heptanedioic acid (pimelic acid) and 1,5-pentanediol, was synthesized by polycondensation. The structural characterization of the polyester was done using 1D- and 2D-NMR spectroscopic techniques. The properties of the resulting polyester-like crystallization behavior, enzymatic degradation, thermal stability, etc., were investigated using differential scanning calorimetry, wide-angle X-ray diffraction, scanning electron microscopy and gel-permeation chromatography. Terahertz time-domain spectroscopy was employed to determine the glass transition temperature, which could not be revealed reliably by conventional thermal analysis. The properties of all-odd-polyester-5,7 were compared with a well-known enzymatic degradable polyester (polycaprolactone). The results indicated that polyester-5,7 has a crystal structure similar to PCL, but a much faster degradation rate. The morphology of polyester-5,7 film during enzymatic degradation showed a fibrillar structure and degradation began by surface erosion. (C) Koninklijke Brill NV, Leiden, 2011

109) Novel layer-by-layer procedure for making nylon-6 nanofiber reinforced high strength, tough, and transparent thermoplastic polyurethane composites. 

Author(s): Jiang, SH (Jiang, Shaohua); Duan, GG (Duan, Gaigai); Hou, HQ (Hou, Haoqing); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: ACS APPLIED MATERIALS & INTERFACES  Volume: 4  Issue: 8  Pages: 4366-4372  DOI: 10.1021/am3010225  Published: AUG 2012  
Abstract: We highlight a novel composite fabrication method based on solution casting, electrospinning, and film stacking for preparing highly transparent nylon-6 nanofiber reinforced thermoplastic polyurethane (TPU) composite films. The procedure is simple and can be extended to the other thermoplastics. The morphology of fiber/matrix interface and the properties of composite films were also investigated. The method led to a significant reinforcement in mechanical properties of TPU like tensile strength, E modulus, strain, and toughness just using very small amounts of nylon fibers (about 0.4-1.7 wt %; 150-300 nm diameter). The enhanced mechanical properties were achieved without sacrificing optical properties like transparency of TPU.

108) Functional poly(dimethyl aminoethyl methacrylate) by combination of radical ring-opening polymerization and click chemistry for biomedical applications. 

Author(s): Maji, S (Maji, Samarendra); Mitschang, F (Mitschang, Fabian); Chen, LN (Chen, Lina); Jin, Q (Jin, Qiao); Wang, YX (Wang, Youxiang); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 213  Issue: 16  Pages: 1643-1654  DOI: 10.1002/macp.201200220  Published: AUG 28 2012  
Abstract: In this work, the macromolecular design and modular synthesis of degradable and biocompatible copolymers via radical polymerization and click chemistry is highlighted and the resulting systems are evaluated as gene delivery carriers. Poly(ethylene glycol) (PEG) grafted poly[2-methylene-1,3-dioxepane (MDO)-co-propargyl acrylate (PA)-co-2-(dimethyl aminoethyl methacrylate (DMAEMA)] (MPD) is synthesized using radical polymerization and azide-alkyne click chemistry. The polymers are less cytotoxic and are able to condense plasmid DNA into nanosized particles. The low transfection efficiency of polyplexes in HepG2 cells is significantly improved by mixing Tat peptide with polyplexes.

107) Antimicrobial hydantoin-containing  polyesters. 

Author(s): Tan, LC (Tan, Licheng); Maji, S (Maji, Samarendra); Mattheis, C (Mattheis, Claudia); Zheng, MY (Zheng, Mengyao); Chen, YW (Chen, Yiwang); Caballero-Diaz, E (Caballero-Diaz, E.); Gil, PR (Gil, Pilar Rivera); Parak, WJ (Parak, Wolfgang J.); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 12  Issue: 8  Pages: 1068-1076  DOI: 10.1002/mabi.201100520  Published: AUG 2012  
Abstract: A new N-hydantoin-containing biocompatible and enzymatically degradable polyester with antibacterial properties is presented. Different polyesters of dimethyl succinate, 1,4-butanediol, and 3-[N,N-di(beta-hydroxyethyl)aminoethyl]-5,5- dimethylhydantoin in varying molar ratios are prepared via two-step melt polycondensation. The antibacterially active N-halamine form is obtained by subsequent chlorination of the polyesters with sodium hypochlorite. Chemical structures, thermal properties, and spherulitic morphologies of the copolymers are studied adopting FT-IR, NMR, TGA, DSC, WAXD, and POM. The polyesters exhibit antibacterial activity against Escherichia coli. The adopted synthetic approach can be transferred to other polyesters in a straightforward manner.

106) Low dielectric constant polyimide nanomats by electrospinning.

Author(s): Chen, F (Chen, Fei); Bera, D (Bera, Debaditya); Banerjee, S (Banerjee, Susanta); Agarwal, S (Agarwal, Seema)
Source: POLYMERS FOR ADVANCED TECHNOLOGIES  Volume: 23  Issue: 6  Pages: 951-957  DOI: 10.1002/pat.1997  Published: JUN 2012  
Abstract: The proper combination of material (i.e. fluorinated polyimides) and processing technique (electrospinning) could lead to the formation of polyimides with low dielectric constant, high thermo-oxidative stability and glass transition temperature, and high hydrophobicity. The polyimides in this work were based on 4, 4-bis [3'-trifluoromethyl-4' (4'-amino benzoxy) benzyl] biphenyl (Q) and various fluorinated and non-fluorinated dianhydrides namely benzene-1,2,4,5-tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, benzophenone-3,3',4,4'-tetracarboxylic dianhydride, and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Processing of the polyimides was carried out in poly(amic acid) stage by two different methodselectrospinning and solution casting for comparison purposes. The processing of polyimides by electrospinning led to enhancement in mechanical properties (dianhydride-structure dependent) and hydrophobicity without sacrificing thermo-oxidative stability and glass transition temperatures significantly. Also, low dielectric constants (as low as 1.43) could be attained by suitable combination of dianhydride (6FDA) with 4, 4-bis [3'-trifluoromethyl-4' (4'-amino benzoxy) benzyl] biphenyl diamine. Copyright (C) 2011 John Wiley & Sons, Ltd.

105) Tough and transparent nylon-6 electrospun nanofiber reinforced melamine-formaldehyde composites.

Author(s): Jiang, SH (Jiang, Shaohua); Hou, HQ (Hou, Haoqing); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: ACS APPLIED MATERIALS & INTERFACES  Volume: 4  Issue: 5  Pages: 2597-2603  DOI: 10.1021/am300286m  Published: MAY 2012  
Abstract: The use of nylon-6 electrospun nanofiber mats as reinforcement with synergistic effect in tensile strength and toughness for melamine-formaldehyde (MF) resin is highlighted in this article. Interestingly, there was a drastic effect of the wetting procedure of reinforcing fiber mat by the MF resin on the morphology and mechanical properties of the composites. The wetting of nylon fibers by passing through a solution of MF resin showed a core-shell morphology and a significant improvement in properties as compared to the dip-coating procedure for wetting of the fibers. Depending on the wt% of reinforcing nylon fiber mats, the composites could be considered as either fiber reinforced MF composites or MF glued nylon fibers.

104) First example of a universal and cost-effective approach: polymers with tunable upper critical solution temperature in water and electrolyte solution.

Author(s): Seunng, J (Seunng, Jan); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 45  Issue: 9  Pages: 3910-3918  DOI: 10.1021/ma300355k  Published: MAY 8 2012  
Abstract: We present a powerful universal and versatile approach for the synthesis of polymers that show a UCST in water. Up to now only a few polymers were known that show an upper critical solution temperature (UCST) in water. This study establishes general requirements to obtain polymers with a UCST in water as well as electrolyte solution. It is demonstrated that old homo- and copolymer systems like poly(methacrylamide) and poly(acrylamide-co-acrylonitrile) can exhibit a UCST in water and how polymers with a tunable UCST can be synthesized by copolymerization of acrylamide and acrylonitrile, monomers that are industrially produced on large scales. Controlled increase of the UCST by copolymerization of acryamide with varying amounts of acrylonitrile was shown, and it could be varied between 6 and 60 degrees C. The hysteresis between the cloud point upon cooling and heating was very small with only 1-2 degrees C in most cases. The cloud points in pure water were similar to he cloud points measured in phosphate buffered saline. Also, it is possible to prepare highly concentrated thermoresponsive Polymer solutions without gel formation.

103) Preparation of continuous gold nanowires by electrospinning of high-concentration aqueous dispersions of gold nanoparticles. 

Author(s): Gries, K (Gries, Katharina); Vieker, H (Vieker, Henning); Golzhauser, A (Goelzhaeuser, Armin); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: SMALL  Volume: 8  Issue: 9  Pages: 1436-1441  DOI: 10.1002/smll.201102308  Published: MAY 7 2012  
Abstract: Gold nanowires are prepared by the electrospinning of highly concentrated aqueous dispersions of gold nanoparticles (AuNPs) in the presence of poly(vinyl alcohol) and subsequent annealing at higher temperatures. Continuous wires of sintered AuNPs are obtained as a result of this process. The Au wires are characterized by transmission electron microscopy, helium ion microscopy, optical microscopy, and X-ray diffractometry.

102) Vinyl-functionalized gold nanoparticles as artificial monomers for the free radical copolymerization with methyl methacrylate. 

Author(s): Gries, K (Gries, Katharina); El Helou, M (El Helou, Mira); Witte, G (Witte, Gregor); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: POLYMER  Volume: 53  Issue: 8  Pages: 1632-1639  DOI: 10.1016/j.polymer.2012.02.008  Published: APR 3 2012  
Abstract: Vinyl-functionalized gold nanoparticles (AuNP) were prepared by surface polymerization of vinyl-functionalized ligands induced by carboxy-functionalized radical initiators followed by vinyl-transformation of the carboxy-group. These AuNP were regarded as artificial molecules as they were used as comonomers for the free radical copolymerization with methyl methacrylate (MMA). Successful copolymerization was proven by gel permeation chromatography (GPC) and by thermogravimetrical analysis (TGA). Further analysis of the novel hybrid material was carried out by transmission electron microscopy (TEM) and by atomic force microscopy (AFM) to proof the presence of AuNP and their arrangement. (C) 2012 Elsevier Ltd. All rights reserved.

101) Closing one of the last gaps in polyionene compositions: alkyloxyethylammonium ionenes as fast-acting biocides.

Author(s): Mattheis, C (Mattheis, Claudia); Zheng, MY (Zheng, Mengyao); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 12  Issue: 3  Pages: 341-349  DOI: 10.1002/mabi.201100316  Published: MAR 2012  
Abstract: Alkyloxyethylammonium ionenes are reported as biocompatible biocides with a time of biocidal action within a few minutes. The presence of both ethoxyethyl and aliphatic spacers besides long alkyl chain substituents on the quaternary nitrogen atom differentiates these biocides structurally from the known polyionenes. The influence of alkyl spacer length, counter ion and length of the pendant alkyl groups on the antibacterial properties is studied. E. coli is adopted as a test organism. MIC and MBC values are determined via broth dilution methods; time-dependent tests are accomplished by determining the number of viable cells with the spread-plate method after different contact times. Structural characterization is conducted via NMR and mass spectrometry techniques.

100) Water- stable all-biodegradable microparticles in nanofibers by electrospinning of aqueous dispersions for biotechnical plant protection. 

Author(s): Bansal, P (Bansal, Priyanka); Bubel, K (Bubel, Kathrin); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: BIOMACROMOLECULES  Volume: 13  Issue: 2  Pages: 439-444  DOI: 10.1021/bm2014679  Published: FEB 2012  
Abstract: Pheromone eluting oligolactide (OLA) microcapsules immobilized in electrospun biodegradable polyester nanofibers were obtained by electrospinning of; aqueous dispersions of the microcapsules. OLA was prepared by conventional melt polycondensation of lactic acid. Following the protocol of the solvent displacement method, OLA was dissolved in acetone and mixed with Brij S20 and the pheromone of the European grape vine moth, Lobesia Botrana, (E,Z)-7,9-dodecadien-l-yl acetate (DA). Up to 32 wt % of this mixture could, be dispersed in water with colloidal stability of several weeks without any sedimentation. Without DA as well as OLA, no stable dispersions of OLA in water, were obtained. Replacement of DA by classical hydrophobes typically used for miniemulsions did not yield stable dispersions, but the addition of octyl acetate, which shows structural similarity to DA, yielded stable dispersions in water up to 10 wt 96. Dispersions of OLA/DA were successfully electrospun in combination with an aqueous dispersion of a biodegradable block copolyester resulting in water-stable nanofibers containing OLA/DA microcapsules. Release of DA from microcapsules and fibers was retarded in comparison with non encapsulated DA, as shown by model studies.

99) Design and biophysical characterization of bioresponsive degradable poly(dimethylaminoethyl methacrylate) based polymers for in vitro DNA transfection. 

Author(s): Zhang, Y (Zhang, Yi); Zheng, MY (Zheng, Mengyao); Kissel, T (Kissel, Thomas); Agarwal, S (Agarwal, Seema)
Source: BIOMACROMOLECULES  Volume: 13  Issue: 2  Pages: 313-322  DOI: 10.1021/bm2015174  Published: FEB 2012  
Abstract: Water-soluble, degradable polymers based on poly(N,N-dimethlaminoethyl methacrylate) (PDMAEMA) with low cytotoxicity and good p-DNA transfection efficiency are highlighted in this article. To solve the nondegradability issue of PDMAEMA, new polymers based on DMAEMA and 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) for gene transfection were synthesized. A poly(ethylene oxide) (PEO) azo-initiator was used as free-radical initiator. PEGylation was performed to improve water solubility and to reduce cytotoxicity of the polymers. The resulting polymers contain hydrolyzable ester linkages in the backbone and were soluble in water even with very high amounts of ester linkages. These degradable copolymers showed significantly less backbone and were soluble in water even with very high amount of ester linkages. These degradable copolymers showed significantly less toxicity with a MTT assay using L929 cell lines and demonstrated promising DNA transfection efficiency when compared with the gold standard poly(ethyleneimine). Bioresponsive properties of the corresponding quaternized DMAEMA based degradable polymers were also studied. Although the quaternized DMAEMA copolymers showed enhanced water solubility, they were inferior in gene transfection and toxicity as compared to the unquaternized copolymers.

98) Design and proof of reversible micelle-to-vesicle multistimuli-responsive morphological regulations. 

Author(s): Jin, Q (Jin, Qiao); Luy, C (Luy, Christoph); Ji, J (Ji, Jian); Agarwal, S (Agarwal, Seema)
Source: JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY  Volume: 50  Issue: 3  Pages: 451-457  DOI: 10.1002/pola.25050  Published: FEB 1 2012  
Abstract: Multistimuli-responsive precise morphological control over self-assembled polymers is of great importance for applications in nanoscience as drug delivery system. A novel pH, photoresponsive, and cyclodextrin-responsive block copolymer were developed to investigate the reversible morphological transition from micelles to vesicles. The azobenzene-containing block copolymer poly(ethylene oxide)-b-poly(2-(diethylamino)ethyl methacrylate-co-6-(4-phenylazo phenoxy)hexyl methacrylate) [PEO-b-P(DEAEMA-co-PPHMA)] was synthesized by atom transfer radical polymerization. This system can self-assemble into vesicles in aqueous solution at pH 8. On adjusting the solution pH to 3, there was a transition from vesicles to micelles. The same behavior, that is, transition from vesicles to micelles was also realizable on addition of beta-cyclodextrin (beta-CD) to the PEO-b-P(DEAEMA-co-PPHMA) solution at pH 8. Furthermore, after beta-CD was added, alternating irradiation of the solution with UV and visible light can also induce the reversible micelle-to-vesicle transition because of the photoinduced trans-to-cis isomerization of azobenzene units. The multistimuli-responsive precise morphological changes were studied by laser light scattering, transmission electron microscopy, and UVvis spectra. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 451457, 2012

97) Upper critical solution temperature of poly(N-acryloyl glycinamide) in water: a concealed property.

Author(s): Seuring, J (Seuring, Jan); Bayer, FM (Bayer, Frank M.); Huber, K (Huber, Klaus); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 45  Issue: 1  Pages: 374-384  DOI: 10.1021/ma202059t  Published: JAN 10 2012  
Abstract: Polymers showing an upper critical solution temperature (UCST) in water are rare. Recently, the nonionic homopolymer poly(N-acryloyl glycinamide) (poly(NAGA)) has been shown to exhibit a sharp upper critical solution temperature in pure water as well as in electrolyte solution. Although poly(NAGA) is known for decades the UCST behavior had not been reported. The first controlled radical polymerization of poly(NAGA) by the RAFT (reversible addition fragmentation transfer) process was also achieved recently, but no UCST was observed. The present study shows that traces of ionic groups in the polymer prevent phase separation. Failure to notice the UCST in the past was because ionic groups have been introduced, unintentionally by either acrylate impurities in the monomer, hydrolysis of the polymer side chains, and/or usage of ionic initiators or chain transfer agents. A synthetic procedure for high purity NAGA monomer free of ionic impurities is reported. It is also shown how to obtain stable aqueous solutions of nonionic poly(NAGA) so that the UCST behavior can be exploited in pure water as well as in a physiological milieu. Further, ultrasensitive differential scanning calorimetry and light scattering were used to get insights into the phase separation mechanism. We believe that this knowledge is transferable to other systems and will greatly accelerate research in the field of macromolecules that feature thermally reversible hydrogen bonding.


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96) Functional degradable polymers via radical ring-opening polymerization and click chemistry. 

Author(s): Maji, S (Maji, Samarendra); Zheng, MY (Zheng, Mengyao); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 212  Issue: 23  Pages: 2573-2582  DOI: 10.1002/macp.201100375  Published: DEC 1 2011  
Abstract: The use of free-radical polymerization for the formation of an alkyne-functionalized polymer with ester units of polycaprolactone type in the backbone is shown. This is done by the copolymerization of a cyclic ketene acetal [2-methylene-1,3-dioxepane (MDO)] with propargyl acrylate using a free radical initiator, azobis(isobutyronitrile). Structural characterization of the copolymers using 1D and 2D NMR techniques shows the random distribution and very high percentage of inclusion of alkyne groups onto the polymer backbone. The exemplary grafting of a biocompatible polymer [poly(ethylene glycol)] via azide-alkyne click chemistry is also shown. Hydrolytic degradation behavior and biocompatibility of the polymers (cytotoxicity) studies are also reported.

95) Preparation of gold nanoparticle- poly(l-menthyl methacrylate) conjugates via ATRP polymerization. 

Author(s): Gries, K (Gries, Katharina); Bubel, K (Bubel, Kathrin); Wohlfahrt, M (Wohlfahrt, Malte); Agarwal, S (Agarwal, Seema); Koert, U (Koert, Ulrich); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 212  Issue: 23  Pages: 2551-2557  DOI: 10.1002/macp.201100449  Published: DEC 1 2011  
Abstract: Poly(L-menthyl methacrylate) (PMenMA) is synthesized by atom transfer radical polymerization (ATRP) of methyl L-mentholacrylate using bis[2-(2-bromoisobutyrooxy)ethyl]disulfide] ((BiBOE)(2))S(2)) as the ATRP coinitiator. Reduction of hydrogen tetrachloroaureate(III) (HAuCl(4) center dot 3 H(2)O) by Super-Hydride in the presence of PMenMA yields gold nanoparticles (AuNP)-PMenMA conjugates in the size range of 220 nm, depending on the ratio of PMenMA and HAuCl(4). AuNP-PMenMA is characterized by TEM, NMR, IR-, and UV-spectroscopy. The correlation of the ratio of (AuNP)-PMenMA conjugates and free PMenMA is analyzed by gel permeation chromatography (GPC).

94) Biocompatible drug delivery system for photo-triggered controlled release of 5-fluorouracil. 

Author(s): Jin, Q (Jin, Qiao); Mitschang, F (Mitschang, Fabian); Agarwal, S (Agarwal, Seema)
Source: BIOMACROMOLECULES  Volume: 12  Issue: 10  Pages: 3684-3691  DOI: 10.1021/bm2009125  Published: OCT 2011  
Abstract: The synthesis of a photo-triggered biocompatible drug delivery system on the basis of coumarin-functionalized block copolymers is reported. The coumarin-functionalized block copolymers poly(ethylene oxide)-b-poly- (n-butyl methacrylate-co-4-methyl-[7-(methacryloyl)-oxyethyloxy]coumarin)) (PEO-b-P(BMA-co-CMA)) were synthesized via atom transfer radical polymerization (ATRP) The micelle-drug conjugates were made by covalent bonding of anticancer drug 5-fluorouracil (5-FU) to the coumarin under UV irradiation at wavelength >310 nm. The micelle-drug conjugates, possessed spherical morphology with diameters of 70 nm from TEM images. In vitro drug release experiments showed the controlled release of anticancer drugs 5-FU from the micelle-drug conjugates under UV irradiation (254 nm). These micelle-drug conjugatse showed excellent biocompatibility by the in vitro cytotoxicity experiments. The results suggest that these micelle-drug conjugates could be a promising candidate for the delivery of anticancer agents with low side effects on normal cells and excellent therapeutic efficacy to cancer cells.

93) Electrospun carbon fiber mat with layered architecture for anode in microbial fuel cells. 

Author(s): Chen, SL (Chen, Shuiliang); He, GH (He, Guanghua); Carmona-Martinez, AA (Carmona-Martinez, Alessandro Alfredo); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas); Hou, HQ (Hou, Haoqing); Schroder, U (Schroeder, Uwe)
Source: ELECTROCHEMISTRY COMMUNICATIONS  Volume: 13  Issue: 10  Pages: 1026-1029  DOI: 10.1016/j.elecom.2011.06.009  Published: OCT 2011  
Abstract: Layered carbon fiber mats have been prepared by layer-by-layer (LBL) electrospinning of polyacrylonitrile onto thin natural cellulose paper and subsequent carbonization. The layered carbon fiber mat has been proved to be a promising microbial fuel cell anode for high density layered biofilm propagation and high bioelectrocatalytic anodic current density. (C) 2011 Elsevier B.V. All rights reserved.

92) Precisely designed gold nanoparticles by surface polymerization - artificial molecules as building blocks for novel materials. 

Author(s): Bokern, S (Bokern, Stefan); Gries, K (Gries, Katharina); Gortz, HH (Goertz, Hans-Helmut); Warzelhan, V (Warzelhan, Volker); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: ADVANCED FUNCTIONAL MATERIALS  Volume: 21  Issue: 19  Pages: 3753-3759  DOI: 10.1002/adfm.201100590  Published: OCT 7 2011  
Abstract: The synthesis of gold nanoparticles (2-4 nm) carrying a single functional polystyrene chain and its characterization by gel permeation chromatography are reported. This has been achieved by a new type of macromolecular azo-initiator based on telechelic polystyrene with containing alpha,omega-methylcoumarin endgroups and an azo group in the middle of the polystyrene. The structure and the near-quantitative functionality of the initiator have been verified by performing NMR, GPC, and UV-vis measurements. This macroinitiator has been used to initiate a surface polymerization of 4-vinylthiophenol molecules immobilized on the surface of gold nanoparticles. As a product, gold nanoparticles carrying exactly one polystyrene chain have been synthesized with functionalization degrees of up to 90% (crude yield). Proof and quantification of the functionalization degree have been demonstrated by application of a GPC setup with a diode array detector for online UV-vis spectra.

91) Electrospun PLLA nanofiber scaffolds and their use in combination with BMP-2 for reconstruction of bone defects. 

Author(s): Schofer, MD (Schofer, Markus D.); Roessler, PP (Roessler, Philip P.); Schaefer, J (Schaefer, Jan); Theisen, C (Theisen, Christina); Schlimme, S (Schlimme, Sonja); Heverhagen, JT (Heverhagen, Johannes T.); Voelker, M (Voelker, Maximilian); Dersch, R (Dersch, Roland); Agarwal, S (Agarwal, Seema); Fuchs-Winkelmann, S (Fuchs-Winkelmann, Susanne); Paletta, JRJ (Paletta, Juergen R. J.)
Source: PLOS ONE  Volume: 6  Issue: 9  Article Number: e25462  DOI: 10.1371/journal.pone.0025462  Published: SEP 28 2011  
Abstract: Introduction: Adequate migration and differentiation of mesenchymal stem cells is essential for regeneration of large bone defects. To achieve this, modern graft materials are becoming increasingly important. Among them, electrospun nanofiber scaffolds are a promising approach, because of their high physical porosity and potential to mimic the extracellular matrix (ECM).
Materials and Methods: The objective of the present study was to examine the impact of electrospun PLLA nanofiber scaffolds on bone formation in vivo, using a critical size rat calvarial defect model. In addition we analyzed whether direct incorporation of bone morphogenetic protein 2 (BMP-2) into nanofibers could enhance the osteoinductivity of the scaffolds. Two critical size calvarial defects (5 mm) were created in the parietal bones of adult male Sprague-Dawley rats. Defects were either (1) left unfilled, or treated with (2) bovine spongiosa, (3) PLLA scaffolds alone or (4) PLLA/BMP-2 scaffolds. Cranial CT-scans were taken at fixed intervals in vivo. Specimens obtained after euthanasia were processed for histology, histomorphometry and immunostaining (Osteocalcin, BMP-2 and Smad5).
Results: PLLA scaffolds were well colonized with cells after implantation, but only showed marginal ossification. PLLA/BMP-2 scaffolds showed much better bone regeneration and several ossification foci were observed throughout the defect. PLLA/BMP-2 scaffolds also stimulated significantly faster bone regeneration during the first eight weeks compared to bovine spongiosa. However, no significant differences between these two scaffolds could be observed after twelve weeks. Expression of osteogenic marker proteins in PLLA/BMP-2 scaffolds continuously increased throughout the observation period. After twelve weeks osteocalcin, BMP-2 and Smad5 were all significantly higher in the PLLA/BMP-2 group than in all other groups.
Conclusion: Electrospun PLLA nanofibers facilitate colonization of bone defects, while their use in combination with BMP-2 also increases bone regeneration in vivo and thus combines osteoconductivity of the scaffold with the ability to maintain an adequate osteogenic stimulus.

90) Many-sided nanofiber structures through electrospinning. 

Wendorff, J. H., Agarwal, S., Greiner, A. Nachrichten aus der Chemie 2011, 59(7/8), 714.


89) Quick polymerization from electrospun macroinitiators for making thermoresponsive nanofibers. 

Author(s): Brandl, C (Brandl, Christian); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 296  Issue: 9  Pages: 858-864  DOI: 10.1002/mame.201100031  Published: SEP 14 2011  
Abstract: Thermoresponsive nanofibers by very fast grafting of N,N-isopropylacrylamide (NIPAAm) from electrospun atom transfer radical polymerization (ATRP) macroinitiator are presented in this work. The heterogenous grafting of NIPAAm onto macroinitiator fibers could be done in few minutes, i.e., in less than 5 min. The procedure involved electrospinning of an ATRP macroinitiator and subsequent PNIPAAm grafting using "grafting from" technique. The ATRP Macroinitiator was based on a copolymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA). The growth of the PNIPAAm layer on electrospun fibers was followed by IR-spectroscopy and SEM analysis. The temperature-dependent-phase transition was proven by contact angle measurements and could be shown on the same surface for many cycles.

88) Electrospinning and cutting of ultrafine bioerodible poly(lactide-co-ethylene oxide) tri- and multiblock copolymer fibers for inhalation applications. 

Author(s): Thieme, M (Thieme, Marcel); Agarwal, S (Agarwal, Seema); Wendorff, JH (Wendorff, Joachim H.); Greiner, A (Greiner, Andreas)
Source: POLYMERS FOR ADVANCED TECHNOLOGIES  Volume: 22  Issue: 9  Pages: 1335-1344  DOI: 10.1002/pat.1617  Published: SEP 2011  
Abstract: Triblock copolymers made up of poly(ethylene oxide) (PEO) and polylactide (PLA) were synthesized and converted to fibers by the electrospinning process. A two-step in situ-synthesis in bulk was applied to extend PLA-PEO-PLA triblock copolymers with relatively short block length and low molecular weight in order to obtain electrospinnable materials. DL-lactide was polymerized to the hydroxyl chain ends of PEO via the stannous octoate route. Hexamethylene diisocyanate (HDI) was added as chain extender in the second step, leading to poly(ether-ester-urethane) multiblock copolymers. The materials were electrospun from solutions in chloroform. Different concentrations and voltages were analyzed. The ether and ester blocks were varied in their block length and their effects on the fiber morphology was studied. Variations in the electrical conductivity of the chloroform solutions were investigated by adding triethyl benzyl ammonium chloride (TEBAC) in different amounts. Finally, with high quality electrospun PLA-PEO-PEO triblock copolymer fibers mechanical cutting was possible. Copyright (C) 2009 John Wiley & Sons, Ltd.

87) N-Acryloyl glycinamide. 

Author(s): Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema); Harms, K (Harms, Klaus)
Source: ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE  Volume: 67  Pages: O2170-U1736  DOI: 10.1107/S1600536811029758  Part: 8  Published: AUG 2011  
Abstract: The molecule of the title compound [systematic name: N-(carbamoylmethyl)prop-2-enamide], C5H8N2O2, which can be radically polymerized to polymers with thermoresponsive behavior in aqueous solution, consists of linked essentially planar acrylamide and amide segments [maximum deviations = 0.054 (1) and 0.009 (1) angstrom] with an angle of 81.36 (7)degrees between their mean planes. In the crystal, N-H center dot center dot center dot O hydrogen bonding leads to an infinite two-dimensional network along (100).

86) Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on growth and osteogenic differentiation of human mesenchymal stem cells. 

Author(s): Schofer, MD (Schofer, Markus D.); Veltum, A (Veltum, Anne); Theisen, C (Theisen, Christina); Chen, F (Chen, Fei); Agarwal, S (Agarwal, Seema); Fuchs-Winkelmann, S (Fuchs-Winkelmann, Susanne); Paletta, JRJ (Paletta, Juergen R. J.)
Source: JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE  Volume: 22  Issue: 7  Pages: 1753-1762  DOI: 10.1007/s10856-011-4341-4  Published: JUL 2011  
Abstract: Mesenchymal stem cell differentiation of osteoblasts is triggered by a series of signaling processes including integrin and bone morphogenetic protein (BMP), which therefore act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in an artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffold. Matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were seeded with human mesenchymal stem cells (hMSC) and cultivated over a period of 22 days, either under growth or osteoinductive conditions. During the course of culture, gene expression of alkaline phosphatase (ALP), osteocalcin (OC) and collagen I (COL-I) as well as Smad5 and focal adhesion kinase (FAK), two signal transduction molecules involved in BMP-2 or integrin signaling were analyzed. Furthermore, calcium and collagen I deposition, as well as cell densities and proliferation, were determined using fluorescence microscopy. The incorporation of BMP-2 into PLLA-collagen type I nanofibers resulted in a decrease in diameter as well as pore sizes of the scaffold. Mesenchymal stem cells showed better adherence and a reduced proliferation on BMP-containing scaffolds. This was accompanied by an increase in gene expression of ALP, OC and COL-I. Furthermore the presence of BMP-2 resulted in an upregulation of FAK, while collagen had an impact on the gene expression of Smad5. Therefore these different strategies can be combined in order to enhance the osteoblast differentiation of hMSC on PLLA based nanofiber scaffold. By doing this, different signal transduction pathways seem to be up regulated.

85) Degradable elastomeric block copolymers based on polycaprolactone by free-radical chemistry.

Author(s): Grabe, N (Grabe, Norman); Zhang, Y (Zhang, Yi); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 212  Issue: 13  Pages: 1327-1334  DOI: 10.1002/macp.201100031  Published: JUL 1 2011  
Abstract: New degradable, transparent, and elastomeric materials based on PCL are reported in this work. These are block copolymers of PCL with a copolymer of MMA and MDO, i.e. P(MMA-co-MDO)-b-PCL-b-P(MMA-co-MDO). A PCL-based macro-azoinitiator is used for preparing the block copolymers by free-radical chemistry. The free-radical copolymerization of MDO with MMA provides CL units distributed randomly on the PMMA backbone of the second block. This provides the advantage of bringing degradability to the whole system. The detailed structural characterization of the new polymers, their properties evaluation like thermal and mechanical are also reported. The materials are degradable, transparent, and elastomeric depending upon the copolymer composition and block length.

84) Phantom ring-closing condensation polymerization: towards antibacterial oligoguanidines.

Author(s): Mattheis, C (Mattheis, Claudia); Schwarzer, MC (Schwarzer, Martin C.); Frenking, G (Frenking, Gernot); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 32  Issue: 13  Pages: 994-999  DOI: 10.1002/marc.201100123  Published: JUL 1 2011  
Abstract: The first example of phantom ring-closing condensation polymerization for the synthesis of oligoguanidines is presented. A new oligoguanidine with a ring structure was achieved in one step by the condensation reaction of a triamine, like diethylenetriamine, with guanidine hydrochloride. The condensation reaction proceeded by selective ring-closure towards the formation of five-membered rings in the oligomer backbone. The resulting polymer repeat unit structure was different from the starting monomers (phantom polymer) and was formed by elimination of three molecules of ammonia per repeat unit. The inter-, intra-, and intermolecular reaction sequences led to the new structure as proved by different spectroscopic techniques (atmospheric pressure chemical-ionization mass spectrometry, and one-dimensional and two-dimensional homo- and heteronuclear correlation NMR experiments) as well as supported by quantum chemical investigations. Preliminary results regarding antibacterial use of the resulting oligoguanidine were also promising and showed its effect within 15-30 min as an antibacterial material.

83) Synthesis of new thermoplastic elastomers by silver nanoparticles as cross-linker.

Author(s): Bokern, S (Bokern, Stefan); Fan, ZY (Fan, Ziyin); Mattheis, C (Mattheis, Claudia); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 44  Issue: 12  Pages: 5036-5042  DOI: 10.1021/ma200738b  Published: JUN 28 2011  
Abstract: A novel type of elastomers with silver nanoparticles (AgNP) as cross-linkers has been obtained by a quantitative one-phase bottom-up procedure based on alpha,omega-dimercapto-poly(cis-1,4-isoprene) (PIP). This telechelic polymer with high cis-content of >80% and near-quantitative fiinctionalization degree has been synthesized in a one-pot procedure by anionic polymerization. It was cross-linked by coordination of the thiol groups to in-situ synthesized AgNP to yield a repeatedly melt-processable elastomer. It was found that the E-modulus increased up to an ideal ratio of AgNP to PIP and decreases drastically with AgNP oversaturation due to decreasing cross-linking density. Swelling experiments were in agreement with these results. The cross-linking of telechelic polymers with metal nanoparticles has been applied to other metals and polymers, leading to cross-linked materials in all cases. Antibacterial properties of the silver-containing elastomers were found by the Kirby-Bauer test.

82) Stimuli-responsive elastic polyurethane-based superabsorber nanomat composites.

Author(s): Chen, F (Chen, Fei); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 296  Issue: 6  Pages: 517-523  DOI: 10.1002/mame.201000387  Published: JUN 16 2011  
Abstract: Photoresponsive superabsorber particles containing a crosslinked hydrophilic core and a hydrophobic azobenzene-containing shell were used to prepare photoresponsive polymeric nanomats, thus combining photoresponsivity with high porosity, toughness, and hydrophilicity. The properties of the nanomat composites were highly dependent upon the amount of the superabsorber photochromic particles added. Stable, highly elastic composite nanomats with very high loading (up to approximate to 50 wt.-%), good water absorption capacity (4000%) and relatively good tensile strength (3 MPa) were obtained. The photoresponsive behavior of the composites is demonstrated, which leads to relatively fast water desorption.

81) Incorporation of osteoblasts (MG63) into 3D nanofiber matrices by simultaneous electrospinning and electrospraying in bone tissue engineering. 

Author(s): Paletta, JRJ (Paletta, J. R. J.); Mack, F (Mack, F.); Schenderlein, H (Schenderlein, H.); Theisen, C (Theisen, C.); Schmitt, J (Schmitt, J.); Wendorff, JH (Wendorff, J. H.); Agarwal, S (Agarwal, S.); Fuchs-Winkelmann, S (Fuchs-Winkelmann, S.); Schofer, MD (Schofer, M. D.)
Source: EUROPEAN CELLS & MATERIALS  Volume: 21  Published: JAN-JUN 2011  
Abstract: Nanofibre scaffolds are suitable tools for bone tissue engineering. Mimicking the extracellular matrix, they allow for cell growth and differentiation. However, in large 3D scaffolds, uniform cell colonisation presents an unsolved problem. Our aim was to design and analyse a method of colonising nanofibre scaffolds, combining electrospinning of fibres and electrospraying of cells, to determine its impact on cell survival, growth, and gene expression. The osteoblast-like cell line MG63 was suspended in medium and electrosprayed into growing scaffolds of poly-(l-lactic acid) (PLLA) or PLLA/Col-I blend nanofibres. Fluorescein diacetate (FDA) staining was used to determine survival and growth over a 22 d culture period. Expression of osteocalcin (OC) and type I collagen (Col-I) genes was determined by real time PCR. Fluorescence microscopy was used to analyse Col-I and OC deposition, as well as cell densities. While spraying distance and cell density in the spraying solution influenced survival and cell density, the combination of electrospinning and electrospraying did not negatively influence the maintenance of the osteoblast phenotype. Furthermore, VEGF induction in response to hypoxia was not suppressed, but modulated by polymer composition. Therefore, simultaneous electrospinning and electrospraying is a suitable tool in producing nanofibre based 3D cell seeded scaffolds.

80) Electrospun and solution blown three-dimensional carbon fiber nonwovens for application as electrodes in microbial fuel cells.

Author(s): Chen, SL (Chen, Shuiliang); Hou, HQ (Hou, Haoqing); Harnisch, F (Harnisch, Falk); Patil, SA (Patil, Sunil A.); Carmona-Martinez, AA (Carmona-Martinez, Alessandro A.); Agarwal, S (Agarwal, Seema); Zhang, YY (Zhang, Yiyun); Sinha-Ray, S (Sinha-Ray, Suman); Yarin, AL (Yarin, Alexander L.); Greiner, A (Greiner, Andreas); Schroder, U (Schroeder, Uwe)
Source: ENERGY & ENVIRONMENTAL SCIENCE  Volume: 4  Issue: 4  Pages: 1417-1421  DOI: 10.1039/c0ee00446d  Published: APR 2011  
Abstract: Three-dimensional carbon fiber electrodes prepared by electrospinning and solution blowing are shown to be excellent electrode materials for bioelectrochemical systems such as microbial fuel cells or microbial electrolysis cells. The bioelectrocatalytic anode current density is shown to reach values of up to 30 A m(-2), which represents the highest reported values for electroactive microbial biofilms.

79) Synthesis of high-molecular-weight tulipalin-a-based polymers by simple mixing and heating of comonomers.

Author(s): Agarwal, S (Agarwal, Seema); Kumar, R (Kumar, Rimpu)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 212  Issue: 6  Pages: 603-612  DOI: 10.1002/macp.201000673  Published: MAR 15 2011  
Abstract: The preparation of a polymer based on Tulipalin A with degradable ester linkages and high glass transition temperature with good processability, and solubility in various organic solvents is reported. The reaction was performed by mixing Tulipalin A and 2-methylene1,3- dioxepane (MDO) at high temperatures (70 degrees C and above) in the entire composition range without any initiator. The polymerization mechanism is found to be different from mere thermal initiation at high temperature. It was a combination of ionic and radical mechanism as proved by different methods. Microstructure analysis was done by 1D and 2D NMR techniques. The reactions were also tuned for different structures with varied properties by adding either the radical trapping agent or radical generators in the system.

78) Polymer/bacteria composite nanofiber nonwovens by electrospinning of living bacteria protected by hydrogel microparticles. 

Author(s): Gensheimer, M (Gensheimer, Marco); Brandis-Heep, A (Brandis-Heep, Astrid); Agarwal, S (Agarwal, Seema); Thauer, RK (Thauer, Rudolf K.); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 11  Issue: 3  Pages: 333-337  DOI: 10.1002/mabi.201000310  Published: MAR 10 2011  
Abstract: Physically crosslinked PVA-hydrogel microparticles are utilized for encapsulation of E. coli and M. luteus. The bacteria survive dry storage or treatment with bacteria-hostile organic solvents significantly better than unprotected bacteria as proven by culture-test experiments. The bacteria-protecting PVA microparticles are available for standard polymer-solution-processing techniques, as exemplarily shown by co-electrospinning of living bacteria encapsulated in dry PVA-hydrogel microparticles together with PVB-, PLLA-, and PCL-form organic solvents.

77) On the way to clean and safe electrospinning-green electrospinning: emulsion and suspension electrospinning.

Author(s): Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: POLYMERS FOR ADVANCED TECHNOLOGIES  Volume: 22  Issue: 3  Special Issue: SI  Pages: 372-378  DOI: 10.1002/pat.1883  Published: MAR 2011  
Abstract: For the process of electrospinning, either water or organic solvents are used as solvents depending upon the solubility of the materials to be spun. For many applications, such as tissue engineering, biomedical, agricultural, etc., the toxicity of the organic solvent used could be highly critical. Besides this, the high viscosities of such polymer solutions even for low weight per cent (wt%) polymer solutions (generally for conventional electrospinning a maximum of 10-15wt% polymer solution can be used) prevent high polymer concentrations and thereby reduces the productivity of the electrospinning process. This justifies the need for an approach which would alleviate concerns regarding safety, toxicology, and environmental problems, in addition, would also overcome the restrictions of too high polymer concentrations of polymer solutions. The answer could be suspension electrospinning. The term suspension electrospinning is referred to the electrospinning of aqueous dispersions (lattices) of water insoluble polymers and is defined in this article as Green Electrospinning. The present mini review highlights the efforts in this promising area of Emulsion and Suspension Electrospinning including their chances and limitations. Copyright (C) 2011 John Wiley & Sons, Ltd.

76) Polymer grafted silver and copper nanoparticles with exceptional stability against aggregation by a high yield one-pot synthesis.

Author(s): Bokern, S (Bokern, Stefan); Getze, J (Getze, Julia); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: POLYMER  Volume: 52  Issue: 4  Pages: 912-920  DOI: 10.1016/j.polymer.2010.12.031  Published: FEB 17 2011  
Abstract: A straightforward synthesis of silver nanoparticles (mean diameters well below 4 nm) with a "graft-to" polystyrene shell (PS@Ag) is described and different synthesis routes are compared. In addition to standard methods like TEM, XRD, UV/Vis and DSC the hybrid material has also been characterized by gel permeation chromatography (GPC).
Long-term stable hybrid materials with silver contents up to 18 wt-% have been realized. The exceptional stability allows industrial-scale processing by melt extrusion. No aggregation or agglomeration of silver nanoparticles is observed after melt co-extrusion with conventional polystyrene at 190 C. The co-extruded blends with silver nanoparticle contents up to 1 wt-% show a homogenous dispersion of nanoparticles in the polystyrene matrix. The synthesis route has also been applied to PS-block-PMMA stabilized silver nanoparticles and to copper to yield polystyrene-stabilized copper nanoparticles with diameters well below 3 nm. (C) 2011 Elsevier Ltd. All rights reserved.

75) Polymer-bound 4-methylcoumarin/1-heptanoyl-5-fluorouracil photodimers: NMR elucidation of dimer structure
Author(s): Sinkel, C (Sinkel, Carsten); Schwarzer, MC (Schwarzer, Martin C.); Frenking, G (Frenking, Gernot); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MAGNETIC RESONANCE IN CHEMISTRY  Volume: 49  Issue: 2  Pages: 70-75  DOI: 10.1002/mrc.2711  Published: FEB 2011  
Abstract: Heterodimers based on the polymer-bound chromophore 4-methylcoumarin and the prodrug 1-heptanoyl-5-fluorouracil, synthesized by photochemical [2 + 2]-cycloaddition are promising photoresponsive drug depots. Drug release experiments are one possibility to deliver proof of a successful reversible drug immobilization, whereas NMR spectroscopy is a potent tool for further structural characterization of these polymer-bound heterodimers. In case of the random copolymer poly(methyl methacrylate-co-7-(2'-methacryloyloxyethoxy)-4-methylcoumarin) three dimers have been identified of which the syn head-to-tail was the predominant one. In contrast, only the syn head-to-head dimer was formed in reasonable yield when the 4-methylcoumarin monofunctionalized pMMA was used as the base polymer. 1D and 2D NMR spectroscopic techniques combined with some theoretical calculations helped in successfully closing one major gap concerning polymer bound 4-methylcoumarin/1-heptanoyl-5-fluorouracil heterodimers that are of potential use in photoresponsive drug delivery devices. Copyright (C) 2011 John Wiley & Sons, Ltd.


74) Use of reactive and functional hydrophobes (hydrophobins) in miniemulsion polymerization of styrene and methyl methacrylate.

Author(s): Agarwal, S (Agarwal, Seema); Grabe, N (Grabe, Norman)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 212  Issue: 4  Pages: 391-400  DOI: 10.1002/macp.201000638  Published: FEB 15 2011  
Abstract: The successful use of multitasking polycaprolactone-based hydrophobins for miniemulsion polymerization of model monomers like styrene and methyl methacrylate is demonstrated. These hydrophobins were synthesized in two steps - the synthesis of polyester diol (i.e., polycaprolactone diol) followed by polycondensation with an equimolar amount of azobis(cyanopentanoic acid dichloride). The hydrophobin, besides acting as a hydrophobe and initiator for the miniemulsion polymerization, also provided functionality; in this case degradability to the miniemulsion. An optimum ratio of hydrophobin to monomer was required for making stable dispersions of a small size (average diameter around 100 nm) with relatively high solid content (around 22%).

73) Living characteristics of the free-radical ring-closing polymerization of diallyldimethylammonium chloride.

Author(s): Blinco, JP (Blinco, James P.); Greiner, A (Greiner, Andreas); Barner-Kowollik, C (Barner-Kowollik, Christopher); Agarwal, S (Agarwal, Seema)
Source: EUROPEAN POLYMER JOURNAL  Volume: 47  Issue: 1  Pages: 111-114  DOI: 10.1016/j.eurpolymj.2010.10.025  Published: JAN 2011  
Abstract: In this communication we provide the most recent results on RAFT-mediated ring-closing polymerization of diallyldimethylammonium chloride (DADMAC) The polymerization was carried out in aqueous solution employing 2 2`-azobis(2-methylpropionamidine)-dihydrochloride as the free radical initiator and trithiocarbonate RAFI' agent (2-{[(dodecylsulfanyl)carbonothioyl sulfanyl]}propanoic acid DoPAT) as the controlling RAFT agent The results show that - while the system is not as completely controlled as previously described - it is nevertheless possible to mediate the polymerization of DADMAC and impart some living characteristics onto the system The initial study on the RAFT-mediated polymerization of DADMAC may have overestimated the degree of livingness within this reaction However it is possible - at low conversions - for some living characteristics to be observed as the evolution of molecular weight with conversion is linear In addition polymers with a reasonably narrow polydispersity can be Isolated (c) 2010 Elsevier Ltd All rights reserved


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72) Novel 'nano in nano' composites for sustained drug delivery: biodegradable nanoparticles encapsulated into nanofiber non-wovens.
Author(s): Beck-Broichsitter, M (Beck-Broichsitter, Moritz); Thieme, M (Thieme, Marcel); Nguyen, J (Nguyen, Juliane); Schmehl, T (Schmehl, Thomas); Gessler, T (Gessler, Tobias); Seeger, W (Seeger, Werner); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas); Kissel, T (Kissel, Thomas)
Source: MACROMOLECULAR BIOSCIENCE  Volume: 10  Issue: 12  Pages: 1527-1535  DOI: 10.1002/mabi.201000100  Published: DEC 8 2010  
Abstract: Novel 'nano in nano' composites consisting of biodegradable polymer nanoparticles incorporated into polymer nanofibers may efficiently modulate drug delivery. This is shown here using a combination of model compound-loaded biodegradable nanoparticles encapsulated in electrospun fibers. The dye coumarin 6 is used as model compound for a drug in order to simulate drug release from loaded poly(lactide-co-glycolide) nanoparticles. Dye release from the nanoparticles occurs immediately in aqueous solution. Dye-loaded nanoparticles which are encapsulated by electrospun polymer nanofibers display a significantly retarded release.

71) Nanofibers by green electrospinning of aqueous suspensions of biodegradable block copolyesters for applications in medicine, pharmacy and agriculture.

Author(s): Sun, JY (Sun, Jinyuan); Bubel, K (Bubel, Kathrin); Chen, F (Chen, Fei); Kissel, T (Kissel, Thomas); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 31  Issue: 23  Pages: 2077-2083  DOI: 10.1002/marc.201000379  Published: DEC 1 2010  
Abstract: Poly(hexamethylene adipate)-PEO block copolymers (PHA-b-PEO) with different PEO contents were synthesized and processed to aqueous suspensions with high solid contents by a solvent displacement method followed by dialysis. The best suspension displayed a solid content of 16 wt.-% and an average particle size of 108 nm. This suspension was mixed with a small amount of high molecular weight PEO and Brij78 and electrospun into corresponding nanofibers. After extraction with water, nanofibers of PHA-b-PEO were obtained. Electrospinning of aqueous suspensions of biodegradable polyesters alleviates concerns regarding safety, toxicology and environmental problems, which are associated with spinning of such polyesters from harmful organic solvents and thereby offers novel perspectives for applications in medicine, pharmacy and agriculture. Electrospinning of polymers from aqueous suspensions avoiding harmful organic solvents is suggested to be "green electrospinning''.

70) Non-ionic homo- and copolymers with h-donor and h-acceptor units with an UCST in water.

Author(s): Seuring, J (Seuring, Jan); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 211  Issue: 19  Pages: 2109-2117  DOI: 10.1002/macp.201000147  Published: OCT 1 2010  
Abstract: A well-studied example of a thermoresponsive polymer is PNiPAAm, which exhibits a sharp coil-to-globule transition in water at its LCST. A study relating to the missing counterpart of LCST polymers is presented: N-acryloylglycinamide (NAGA) homopolymer and copolymers from NAGA and N-acetylacrylamide (NAcAAm) that show a sharp UCST (where the sharpness depends on the composition). The polymers were synthesized by free-radical copolymerization and the copolymerization parameters were determined by the method of Kelen-Tudos. The UCST was investigated by turbidimetry, regarding the influence of the copolymer composition, the polymer concentration and the addition of electrolytes.

69) Gradient nanowires and nanotubes.

Author(s): Agarwal, S (Agarwal, S.); Eckhardt, B (Eckhardt, B.); Grossmann, F (Grossmann, F.); Greiner, A (Greiner, A.); Goring, P (Goering, P.); Wehrspohn, RB (Wehrspohn, R. B.); Wendorff, J (Wendorff, J.)
Source: PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS  Volume: 247  Issue: 10  Pages: 2451-2457  DOI: 10.1002/pssb.201046240  Published: OCT 2010  
Abstract: Different routes to prepare gradient nanowire and nanotubes are presented including the use of polymeric and metal nanoparticles. In the case of electrospinning, latex particles have been added to electrospinning solution. The properties of the fibres have been studied theoretically and experimentally. In the case of face-to-face-wetting of porous templates, solution as well as melt wetting for different polymeric composition from both sides of the template is carried out. It turned out that solution wetting leads to an intermixing of the compounds whereas as melt wetting leads to sharp compositional interfaces. The method has been extended to include plasmonic and magnetic nanoparticles for nanophotonic applications.
(C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

68) A polymeric drug depot based on 7-(2′-methacryloyloxyethoxy)-4-methylcoumarin copolymers for photoinduced release of 5-fluorouracil designed for the treatment of secondary cataracts.

Author(s): Sinkel, C (Sinkel, Carsten); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 211  Issue: 17  Pages: 1857-1867  DOI: 10.1002/macp.201000206  Published: SEP 1 2010  
Abstract: The synthesis of a polymeric, photoresponsive drug-delivery system on the basis of 4-methylcoumarin-side-chain-functionalized methacrylic copolymers with different degrees of functionalization is reported. Drug-release experiments in solution indicated a maximum release of 22 mu g of 5-fluorouracil per 1 mg of polymer. Polymer analogous photochemical drug immobilization does not lead to observable intermolecular cross-linking. Miscibility experiments with PMMA suggest that the bulk polymerization of homogeneous, transparent polymer sheets for intraocular lens fabrication, using MMA as the matrix monomer and incorporating the polymer-drug conjugates as a functional component, is possible.

67) Chemistry, chances and limitations of the radical ring-opening polymerization of cyclic ketene acetals for the synthesis of degradable polyesters.

Author(s): Agarwal, S (Agarwal, Seema)
Source: POLYMER CHEMISTRY  Volume: 1  Issue: 7  Pages: 953-964  DOI: 10.1039/c0py00040j  Published: SEP 2010  
Abstract: This article highlights the progress in the field of radical ring-opening polymerization (RROP) of cyclic ketene acetals for the synthesis of functionalised polyesters, (bio)degradable vinyl polymers, and speciality designed degradable polymers. The method of radical ring-opening polymerization offers the advantage in either making special functional polyesters which are not possible by conventional methods or for making polyesters for special applications where low volume shrinkage is of utmost importance. Furthermore, the beauty of radical ring-opening polymerization is in making a new class of degradable materials called poly(vinyl-co-ester)s. Having ester linkages distributed onto the vinyl polymer backbone is emphasised, no other method can combine vinyl polymer backbone with ester units in a random way. The method has opened new opportunities of using the known biomaterials for degradable applications. Other possibilities and challenges in using this method are making specialised degradable materials like ionomers and polymeric-inorganic hybrid materials, which are also discussed in detail.

66) Chemistry on electrospun polymeric nanofibers: merely routine chemistry or a real challenge.

Author(s): Agarwal, S (Agarwal, Seema); Wendorff, JH (Wendorff, Joachim H.); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 31  Issue: 15  Pages: 1317-1331  DOI: 10.1002/marc.201000021  Published: AUG 3 2010  
Abstract: Nanofiber-based non-wovens can be prepared by electrospinning. The chemical modification of such nanofibers or chemistry using nanofibers opens a multitude of application areas and challenges. A wealth of chemistry has been elaborated in recent years on and with electrospun nanofibers. Known methods as well as new methods have been applied to modify the electrospun nanofibers and thereby generate new materials and new functionalities. This Review summarizes and sorts the chemistry that has been reported in conjunction with electrospun nanofibers. The major focus is on catalysis and nanofibers, enzymes and nanofibers, surface modification for biomedical and specialty applications, coatings of fibers, crosslinking, and bulk modifications. A critical focus is on the question: what could make chemistry on or with nanofibers different from bulk chemistry?

65) Vinyl-type polymerization of alkylester-substituted norbornenes without endo/exo separation.

Author(s): Muller, K (Mueller, Kerstin); Jung, Y (Jung, Youngsuk); Yoon, DY (Yoon, Do Y.); Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 211  Issue: 14  Pages: 1595-1601  DOI: 10.1002/macp.200900647  Published: JUL 15 2010  
Abstract: The vinyl-type homo- and copolymerization of 9-norborn-5-en-2yl-nonane acid ethyl ester and 2-hexyl-5-norbornen was investigated. Both monomers were polymerized using di-mu-chlorobis(6-methoxybicyclo[2.2.1]hept-2-ene-endo-5 sigma,2 pi)palladium(II) and AgSbF(6) as catalysts. Poly(2-hexyl-5-norbornene) is soluble in common organic solvents and has a T(g) of 252 degrees C. Poly(9-norborn-5-en-2yl-nonane acid ethyl ester) shows swelling in solvents like THF, chlorobenzene or chloroform and has a T(g) of 136 degrees C. The solubility of the copolymers depends on the amount of 9-norborn-5-en-2yl-nonane acid ethyl ester. E-modulus measurements of copolymers with different amounts of ester showed an increase of flexibility when increasing the content of 9-norborn-5-en-2yl-nonane acid ethyl ester in the copolymer.

64) Synthesis, characterization and properties of a new polymerisable surfactant: 12-Methacryloyl dodecylphosphocholine.
Author(s): Seuring, J (Seuring, Jan); Reiss, P (Reiss, Philipp); Koert, U (Koert, Ulrich); Agarwal, S (Agarwal, Seema)
Source: CHEMISTRY AND PHYSICS OF LIPIDS  Volume: 163  Issue: 4-5  Pages: 367-372  DOI: 10.1016/j.chemphyslip.2010.03.001  Published: MAY 2010  
Abstract: A new polymerizable surfactant, 12-methacryloyl dodecylphosphocholine (MDPC), has been synthesized using a three-step procedure in moderate yield. Phase transitions were characterized by DSC and phase behavior in water was determined by surface tension and polarizing microscopy. MDPC showed typical surfactant behavior and self-aggregated to micelles above a distinct concentration. The critical micelle concentration (CMC) of MDPC was determined to be 5 x 10(-4) mol/L MDPC showed mesomorphic properties between 75 and 86 degrees C as studied by differential scanning calorimetry (DSC). The formation of black lipid membranes was further investigated. The methacrylate functionalized MDPC could form a bilayer membrane (BLM) although it was very unstable (collapsed after 10-30s). However, it was possible to form stable BLMs in mixture with non-polymerizable two chain phospholipids, i.e. asolectin and diphytanoyl phosphatidylcholine (DPhPC). Stable bilayers could be obtained up to a MDPC content of 50 mol%. Gramicidin A was incorporated into MDPC/DPhPC membranes and exhibited ion-channel activity shown by single channel conductivity measurements. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

63) Non-ionic homo- and copolymers with H-donor and H-acceptor units with an UCST in water.

Seuring,J., Agarwal, S. Macromol. Chem. Phys. 2010, 211(19), 2109. DOI: 10.1002/macp.201000147

Abstract: A well-studied example of a thermoresponsive polymer is PNiPAAm, which exhibits a sharp coil-to-globule transition in water at its LCST. A study relating to the missing counterpart of LCST polymers is presented: N-acryloylglycinamide (NAGA) homopolymer and copolymers from NAGA and N-acetylacrylamide (NAcAAm) that show a sharp UCST (where the sharpness depends on the composition). The polymers were synthesized by free-radical copolymerization and the copolymerization parameters were determined by the method of Kelen-Tudos. The UCST was investigated by turbidimetry, regarding the influence of the copolymer composition, the polymer concentration and the addition of electrolytes.


62) Synthesis, characterization and properties of a new polymerisable surfactant: 12-Methacryloyl dodecylphosphocholine

Seuring, J., Reiss P.,Koert, U., Agarwal, S. Chemistry and Physics of Lipids 2010, 163, 367.

DOI: 10.1016/j.chemphyslip.2010.03.001
Abstract: A new polymerizable surfactant, 12-methacryloyl dodecylphosphocholine (MDPC), has been synthesized using a three-step procedure in moderate yield. Phase transitions were characterized by DSC and phase behavior in water was determined by surface tension and polarizing microscopy. MDPC showed typical surfactant behavior and self-aggregated to micelles above a distinct concentration. The critical micelle concentration (CMC) of MDPC was determined to be 5 x 10(-4) mol/L MDPC showed mesomorphic properties between 75 and 86 degrees C as studied by differential scanning calorimetry (DSC). The formation of black lipid membranes was further investigated. The methacrylate functionalized MDPC could form a bilayer membrane (BLM) although it was very unstable (collapsed after 10-30s). However, it was possible to form stable BLMs in mixture with non-polymerizable two chain phospholipids, i.e. asolectin and diphytanoyl phosphatidylcholine (DPhPC). Stable bilayers could be obtained up to a MDPC content of 50 mol%. Gramicidin A was incorporated into MDPC/DPhPC membranes and exhibited ion-channel activity shown by single channel conductivity measurements. (C) 2010 Elsevier Ireland Ltd. All rights reserved.


61) Synthetic route and characterization of main chain ester containing hydrolytically degradable poly(n, n-dimethylaminoethyl methacrylate) based polycations. 

Author(s): Agarwal, S (Agarwal, Seema); Ren, LQ (Ren, Liqun); Kissel, T (Kissel, Thomas); Bege, N (Bege, Nadja)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 211  Issue: 8  Pages: 905-915  DOI: 10.1002/macp.200900579  Published: APR 15 2010  
Abstract: The possibility of introducing hydrolytically cleavable ester linkages onto the poly(N,N-dimethylaminoethyl methacrylate) for the formation of less toxic and degradable polycations is shown in this work. For achieving this aim, the copolymerization behavior of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), with N,N-dimethylaminoethyl methacrylate (DMAEMA) is studied by free radical ring-opening polymerization. Structural characterization is performed using 1D and 2D NMR techniques. Under optimized reaction conditions, quantitative ring-opening of BMDO took place during the copolymerizations leading to the formation of poly(DMAEMA-co-ester)s. Blocky random copolymers were further quaternized by alkyl bromide to generate degradable cation containing polymers. Cytotoxicity results were highly encouraging and showed less cytotoxicity as compared to polyethyleneimine, which was used as a positive control. The formation and characterization of highly stable copolymer/DNA polyplexes is also shown here.

60) Degradable blends of semi-crystalline and amorphous branched poly(caprolactone): effect of microstructure on blend properties. 

Author(s): Agarwal, S (Agarwal, Seema); Speyerer, C (Speyerer, Christian)
Source: POLYMER  Volume: 51  Issue: 5  Pages: 1024-1032  DOI: 10.1016/j.polymer.2010.01.020  Published: MAR 2 2010  
Abstract: The blend properties of semi-crystalline and amorphous polycaprolactone (PCL) are shown here for the first time. The amorphous polycaprolactone (PCLB) having 20% branches was made by radical-ring-opening polymerization of 2-methylene-1,3-dioxepane. The presence of branches led to non-crystallinity in PCLB. The blends were made in solution in entire concentration range and showed some very interesting properties in terms of synergistic effect on crystallinity leading to the increased crystallinity of PCL and induced crystallinity of amorphous PCLB, minima in the % elongation and maxima in spherulite size depending upon the ratio of amorphous and crystalline part. There was a drastic increase in the compostability as compared to pure PCL on adding even low % of amorphous PCLB in the blends without affecting the thermal stability. The addition of PCLB also affected the transparency and it increased exponentially from about 8% at 650 nm for PCL to about 45% for a blend with composition PCL:PCLB 30:70. (C) 2010 Elsevier Ltd. All rights reserved.

59) In vitro study of dexamethasone release from poly(p-xylylene) films. 

Author(s): Hanefeld, P (Hanefeld, Phillip); Agarwal, S (Agarwal, Seema); Kumar, R (Kumar, Rakesh); Greiner, A (Greiner, Andreas)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 211  Issue: 2  Pages: 265-269  DOI: 10.1002/macp.200900537  Published: JAN 19 2010  
Abstract: Stents or metal endoprotheses are currently used to prevent restenosis after percutaneous transluminal angioplasty (PTA). Recently multi-component systems comprising implant applications, e. g., stents, protective and/or a drug containing layers, have found wide-spread application. Permanent and biocompatible stent coatings based on polyp-xylylene) (PPX) films were investigated for their potential to form drug containing reservoirs. The model drug dexamethasone was loaded into films of PPX by solvent treatment. Loading efficiency and in vitro drug release profiles were studied under physiological conditions. Linear release of dexamethasone was observed when PPX/dexamethasone films were coated by an additional PPX film as cover layer.


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58) The reaction of mer-[ScCl3(H2O)3] with pyridine. Crystal structure of [Sc2Cl4(.mu.-OH)2(Py)4]4Py. 

Author(s): Massa, W (Massa, Werner); Agarwal, S (Agarwal, Seema); Grabe, N (Grabe, Norman); Dehnicke, K (Dehnicke, Kurt)
Source: ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE  Volume: 635  Issue: 12  Pages: 1910-1914  DOI: 10.1002/zaac.200900332  Published: 2009  
Abstract: mer-[ScCl3(H2O)(3)] (1) was prepared from aqueous solutions of scandium trichloride by evaporation and subsequent treatment with thionyl chloride at room temperature. The IR spectrum of 1 is in accordance with the meridional arrangement of the chlorido and aqua ligands. Its reaction with excess pyridine yields [Sc2Cl4(mu-OH)(2)(py)(4)]center dot 4py (2.4py), which is characterized by X-ray diffraction: Space group I2/a, Z = 8, lattice dimensions at 193(2) K: a = 2051.3(2), b = 1056.3(7), c = 4389.4(5) pm, beta = 102.967(12)degrees, R-1 = 0.0584. The molecular structure of 2 consists of distorted octahedrally coordinated scandium atoms, which are connected by p-OH groups to form planar Sc2O2 four-membered rings. The coordination of the scandium atoms is completed by two chlorine ligands and by the nitrogen atoms of the pyridine molecules, the latter being in trans-positions to one another. Experiments to use 2 as possible catalyst for ring-opening polymerization of F-caprolactone (ROP) without co-catalysts were not successful.

57) Synthesis of degradable materials based on caprolactone and vinyl acetate units using radical chemistry.

Author(s): Agarwal, S (Agarwal, Seema); Kumar, R (Kumar, Rimpu); Kissel, T (Kissel, Thomas); Reul, R (Reul, Regina)
Source: POLYMER JOURNAL  Volume: 41  Issue: 8  Pages: 650-660  DOI: 10.1295/polymj.PJ2009091  Published: 2009  
Abstract: Present studies are carried out with an aim to make degradable materials based on caprolactone and vinyl acetate units using radical chemistry. Radical ring-opening copolymerization of 2-methylene-1,3-dioxepane (MDO) with vinyl acetate in presence of AIBN initiator at 70 degrees C was carried out to achieve the aim. The copolymerization introduced degradable PCL repeat units onto the C-C backbone of poly(vinyl acetate). Microstructure analysis of the copolymers is done using different 1D and 2D NMR techniques. Complete ring-opening polymerization of MDO to give ester units was observed during copolymerizations. Reactivity ratios were found out by Kelen Tados method and were r(VAc) = 1.53 and r(MDO) = 0.47 leading to statistical introduction of ester linkages onto the polymer backbone. The materials showed varied glass transition temperatures (from 37 to -44 degrees C) depending upon the amount of ester linkages and very high elongations. The hydrolysis products were also tested for cytotoxicity studies in L929 cells and compared with that of known and accepted standard materials like poly(ethyleneimine). The hydrolysed products were non toxic and showed a cell viability > 95%. Keeping in view the combined properties like degradability, non-toxicity and low glass transition temperatures, the resulting materials could therefore be proposed for different applications like degradable gums, coatings etc.

56) Polycaprolactone based novel degradable ionomers by radical ring-opening polymerization of 2-methylene-1,3-dioxepane.

Agarwal, S., Ren, L.  Macromolecules, 2009, 42,1574.

DOI: 10.1021/ma802615f
Abstract: This work reports the first successful synthesis of polycaprolactone (PCL)-based degradable ionomers using free-radical chemistry. Degradable cationic ionomers were synthesized by random radical terpolymerization of 2-methylene-1,3-dioxepane (MDO), methyl methacrylate (MMA), and N,N-dimethylaminoethyl methacrylate (DMAEMA) and followed by quaternization of amine with alkyl bromide. The terpolymerization of MDO, MMA, and DMAEMA led to a polymer with ester group randomly distributed in the polymer chains. The small-angle X-ray scattering (SAXS) analysis, the transmission electron microscope (TEM), and dynamic mechanical analysis (DMA) showed ionic aggregates existing in ionomers. Ionomers quaternized by ethyl bromide showed relative strong ionic interaction and showed aggregates with a diameter around 30 nm, which had a separate glass transition temperature (T(g)) and performed rather as filler material. Ionomers containing 40 mol % of ester group and 20 mol % of ionic group showed biodegradability after being buried in compost.


55) Effect of different bicomponent electrospinning techniques on the formation of polymeric nanosprings.

Author(s): Chen, SL (Chen, Shuiliang); Hou, HQ (Hou, Haoqing); Hu, P (Hu, Ping); Wendorff, JH (Wendorff, Joachim H.); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 294  Issue: 11  Pages: 781-786  DOI: 10.1002/mame.200900139  Published: NOV 12 2009  
Abstract: The effect of different bicomponent electrospinning techniques i.e., off-centered coaxial electrospinning and side-by-side electrospinning, on the formation of tight nanocoils (nanosprings) was studied. Since right balance between the longitudinal compressive forces arising from the shrinking thermoelastic components and the rigidity emerging from the stiff component and conductivity is required for nanospring formation, conductive solutions of flexible and rigid components were used for the electrospinning. Under optimum conditions, nanofiber mats with almost 100% nanospring morphology were generated using off-centered and side-by-side electrospinning techniques. Mechanical properties of aligned nanomats with and without nanosprings, produced at different collecting speeds are provided.

54) Synthesis, characterization, and property evaluations of copolymers of diamantyl methacrylate with methyl methacrylate.

Author(s): Sinkel, C (Sinkel, Carsten); Agarwal, S (Agarwal, Seema); Fokina, NA (Fokina, Natalie A.); Schreiner, PR (Schreiner, Peter R.)
Source: JOURNAL OF APPLIED POLYMER SCIENCE  Volume: 114  Issue: 4  Pages: 2109-2115  DOI: 10.1002/app.30206  Published: NOV 15 2009  
Abstract: This work reports the homo- and copolymerization behavior of previously unknown 4-diamantyl methacrylate (DMA) with vinyl comonomers like methyl methacrylate (MMA); the starting monomer DMA was synthesized in our laboratory using 4-diamantanol and methacryloyl chloride. The structures of the homo- and copolymers were analyzed using NMR techniques. DMA was found to be more reactive than MMA during copolymerization. The reactivity ratios as determined by the Kelen-Tudos method are r(MMA) = 0.58 and r(DMA) = 1.75. The incorporation of a few mol % of diamantyl units into the PMMA backbone led to a significant increase in its thermal stability and glass transition temperature. The polymers with 15 and 42 mol % of DMA units in the copolymers showed increased T(g) values of 126 degrees C and 172 degrees C, respectively. (C) 2009 Wiley Periodicals, Inc. I Appl Polym Sci 114:2109-2115, 2009

53) Electrospinning of manmade and biopolymer nanofibers - progress in techniques, materials, and applications 

Author(s): Agarwal, S (Agarwal, Seema); Greiner, A (Greiner, Andreas); Wendorff, JH (Wendorff, Joachin H.)
Source: ADVANCED FUNCTIONAL MATERIALS  Volume: 19  Issue: 18  Pages: 2863-2879  DOI: 10.1002/adfm.200900591  Published: SEP 23 2009  
Abstract: Electrospinning of nanofibers has developed quickly from a laboratory curiosity to a highly versatile method for the preparation of a wide variety of nanofibers, which are of interest from a fundamental as well as a technical point of view. A wide variety of materials has been processed into individual nanofibers or nanofiber mats with very different morphologies. The diverse properties of these nanofibers, based on different physical, chemical, or biological behavior, mean they are of interest for different applications ranging from filtration, antibacterial coatings, drug release formulations, tissue engineering, living membranes, sensors, and so on. A particular advantage of electrospinning is that numerous non-fiber forming materials can be immobilized by electrospinning in nanofiber nonwovens, even very sensitive biological objects such as virus, bacteria, and cells. The progress made during the last few years in the field of electrospinning is fascinating and is highlighted in this Feature Article, with particular emphasis on results obtained in the authors' research units. Specific areas of importance for the future of electrospinning, and which may open up novel applications, are also highlighted.

52) Living membranes. Bacteria on a pearl chain.

Gensheimer, M., Agarwal, S., Greiner, A. BIOspektrum  2009, 15(2), 164.


51) Supercapacitors based on hybrid carbon nanofibers containing multiwalled carbon nanotubes.

Qiaohui, G., Xiaoping, Z., Xiaoyan, L., Shuiliang, C., Agarwal, S., Greiner, A., Hou, H. Journal of Materials Chemistry 2009, 19(18), 2810.

DOI: 10.1039/b820170f
Abstract: Hybrid carbon nanofibers containing multiwalled carbon nanotubes (CNTs) were produced by electrospinning CNTs suspended in a solution of polyacrylonitrile in N,N-dimethylformamide, followed by carbonization and activation using a hydroperoxide-water steam mixture at 650 degrees C. Transmission electron microscopy and scanning electron microscopy were used to observe the morphology of the CNT-embedded carbon nanofibers. The specific surface area of the nanofibers was measured using the Brunauer-Emmett-Teller method. The electrochemical properties of the nanofibers were characterized by cyclic voltammetry and galvanotactic charge/discharge in 1MH(2)SO(4) electrolyte. The specific capacitance of electric double-layer capacitors containing CNT-embedded carbon nanofibers as electrodes reached 310 F g(-1), which is almost double that obtained for capacitors containing virgin carbon nanofibers as electrodes. The CNTs embedded in the carbonized electrospun nanofibers provide improved conductive pathways for charge transfer in the electrodes and therefore lead to a significantly enhanced specific capacitance.


50) Progress in the field of electrospinning for tissue engineering applications.

Author(s): Agarwal, S (Agarwal, Seema); Wendorff, JH (Wendorff, Joachim H.); Greiner, A (Greiner, Andreas)
Source: ADVANCED MATERIALS  Volume: 21  Issue: 32-33  Pages: 3343-3351  DOI: 10.1002/adma.200803092  Published: SEP 4 2009  
Abstract: Electrospinning is an extremely promising method for the prevention of tissue engineering (TE) scaffolds. This technique provides nonwovens resembling in their fibrillar structures those of the extracellular matrix (ECM), and offering large surface areas, ease of functionalization for various purposes, and controllable mechanical properties. The recent developments toward large-scale productions combined with the simplicity of the process render this technique very attractive. Progress concerning the use of electrospinning for TE applications has advanced impressively. Different groups have tackled the problem of electrospinning for TE applications from different angles. Nowadays, electrospinning of the majority of biodegradable and biocompatible polymers, either synthetic or natural, for TE applications is straightforward. Different issues, such as cell penetration, incorporation of growth and differentiating factors, toxicity or solvents used, productivity, functional gradient, etc. are main points of current considerations. The progress in the use of electrospinning of TE applications is highlighted in this article with focus on major problems encountered and on various solutions available until now.

49) Polymeric nanosprings by bicomponent electrospinning.

Author(s): Chen, SL (Chen, Shuiliang); Hou, HQ (Hou, Haoqing); Hu, P (Hu, Ping); Wendorff, JH (Wendorff, Joachim H.); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 294  Issue: 4  Pages: 265-271  DOI: 10.1002/mame.200800342  Published: APR 14 2009  
Abstract: An enhanced elasticity of electrospun fibers while retaining their strength would be of great benefit for a set of applications (including tissue engineering). One route toward enhanced elasticity may be based on the introduction of curvature, i.e., of buckled or tight nanocoil (nanospring) configurations. The concept investigated in this contribution is to introduce such configurations via a differential shrinkage of a parallel arrangement of a flexible thermoplastic elastomer (polyurethane) component and a rigid thermoplastic component. Core-shell fibers are produced for this purpose by coaxial electrospinning. It is observed that buckling-nanospring formation can be achieved in this way. The morphology of such fibers and also modifications in the conductivity of the spinning solutions have a considerable effect on details of buckling and nanospring formation.


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48) Polymere Nanofasern durch Elektrospinnen - Materialien für neue Anwendungen.

Agarwal, S., Wendorff, J. H., Greiner, A.  Chemie Ingenieur Technik 2008, 80(11), 1671.


47) Use of electrospinning technique for biomedical applications.

Author(s): Agarwal, S (Agarwal, Seema); Wendorff, JH (Wendorff, Joachim H.); Greiner, A (Greiner, Andreas)
Source: POLYMER  Volume: 49  Issue: 26  Pages: 5603-5621  DOI: 10.1016/j.polymer.2008.09.014  Published: DEC 8 2008  
Abstract: The electrospinning technique provides non-wovens to the order of few nanometers with large surface areas, ease of functionalisation for various purposes and superior mechanical properties. Also, the possibility of large scale productions combined with the simplicity of the process makes this technique very attractive for many different applications. Biomedical field is one of the important application areas among others utilising the technique of electrospinning like filtration and protective material, electrical and optical applications, sensors, nanofiber reinforced composites etc. Electrospinning assembly can be modified in different ways for combining materials properties with different morphological structures for these applications. The importance of electrospinning, in general, for biomedical applications like tissue engineering drug release, wound dressing, enzyme immobilization etc. is highlighted in this feature article. The focus is also on the types of materials that have been electrospun and the modifications that have been carried Out in conventional electrospinning apparatus keeping in view the specific needs for various biomedical applications. (c) 2008 Elsevier Ltd. All rights reserved.

46) Short electrospun fibers by UV cutting method.

Author(s): Stoiljkovic, A (Stoiljkovic, Aleksandar); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 293  Issue: 11  Pages: 895-899  DOI: 10.1002/mame.200800171  Published: NOV 12 2008  
Abstract: Short electrospun fibers were obtained by using UV cutting method. Either polymers with double bonds with a photocross-linker (CL) and photoinitiator (PI) or known photochemistry of coumarin ([2 + 2] cycloaddition reaction) without the addition of CL and PI is utilized for making short electrospun fibers. The electrospun fibers were irradiated by UV light in the presence of a mask with a defined width of slits. The uncovered parts of fibers were cross-linked and therefore became insoluble. The non-crosslinked parts were removed by immersion of the fibers into an appropriate solvent. The length of obtained short fibers can be controlled by changing the width of the slits of the employed mask.

45) Synthesis, characterisation and properties evaluation of methylcoumarin end- functionalised poly(methyl methacrylate) for photoinduced drug release. 

Author(s): Sinkel, C (Sinkel, Carsten); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 41  Issue: 10  Pages: 3460-3467  DOI: 10.1021/ma702622p  Published: MAY 27 2008  
Abstract: The synthesis of novel methylcoumarin end-functionalized poly(methyl methacrylate) of different molecular weights using atom transfer radical polymerization (ATRP) is reported. 7-(2'-Bromoisobutyryloxy)4-methylcoumarin was used as the ATRP initiator at 70 degrees C using copper(I) bromide/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The theoretical and experimental number-average molecular weights M-n with narrow polydispersities (M-w/M-n = 1.1-1.4) agreed very well. Photochemical drug loading of the methylcoumarin end-functionalized polymer was performed in solution (chloroform/acetone 1:2) with benzophenone as additional photosensitizer using a 50-fold excess of the pro-drug 1-heptanoyl-5-fluorouracil (H5FU). UV/vis and NMR spectroscopy were used for the characterization of the polymer drug conjugate and indicated an almost quantitative conversion of coumarin moieties into photodimers. The change of polymer properties like thermal stability, glass transition, and molecular weight after photochemical drug immobilization was also studied. The glass transition temperature increased only negligibly, whereas the thermal decomposition commenced at considerably lower temperature for the polymer drug conjugate. The molecular weight distribution of the H5FU-loaded polymer showed no detectable chain degradation due to the applied UV irradiation. The characterization of the photoinduced drug release was investigated for a single photon absorption (SPA) process. The polymer drug conjugate was irradiated at lambda = 266 nm to cleave the cyclobutane linker between the methylcoumarin moiety and the pro-drug H5FU. The drug release was monitored and quantified using high-performance liquid chromatography (HPLC). Assuming quantitative hydrolysis of H5FU, 4.76 mu g of 5-fluorouracil (5FU) per 1 mg of polymer drug conjugate was released on irradiation.

44) Stoichiometric functionalisation of gold nanoparticles in solution through a free radical polymerisation approach. 

Author(s): Kruger, C (Krueger, Christian); Agarwal, S (Agarwal, Seerna); Greiner, A (Greiner, Andreas)
Source: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY  Volume: 130  Issue: 9  Pages: 2710-+  DOI: 10.1021/ja0763495  Published: MAR 5 2008  
Abstract: A new simple concept for the stoichiametrical funclionalization of nanoparticles based on free radical polymerization of vinyl protected nanoparticles is presented. To demonstrate this concept 2-bis(4-vinylphenyl)disulfane was synthesized and used in the synthesis of gold nanoparticles leading to 4-vinylthiophenol functionalized nanoparticles. Simple free radical polymerization of these particles initiated by 4,4'-azobis-(4-cyanopentanoic acid) delivered nanoparticles with a single carboxyl group. These monofunctionalized gold nanoparticles were utilized for chemical preparation of gold nanoparticle dippers as well as for construction of gold nanoparticle arrays via binding to polyallylamine.

43) Polymer tubes with longitudinal composition gradient by face-to-face wetting.

Kriha, O., Goering, P., Milbradt, M., Agarwal, S., Steinhart, M., Wehrspohn, R., Wendorff, J. H., Greiner, A. Chemistry of Materials 2008, 20(3), 1076.

DOI: 10.1021/cm702088v
Abstract: Nanoporous and macroporous templates were simultaneously infiltrated from both of their opposite surfaces using model polymers labeled with fluorescent probes or bearing probe molecules detectable by energy-dispersive X-ray spectroscopy by precursor wetting. Face-to-face wetting with polymeric solutions resulted in partial mixing of both components, leading to tubular nanostructures characterized by a longitudinal composition gradient. Mixing of the components infiltrated from the opposite surfaces could be prevented by face-to-face wetting with polymeric melts, leading to the formation of tubular components predominantly consisting of the pure components that were separated by sharp interfaces.



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42) Biocompatible, thermoresponsive, and biodegradable: simple preparation of "all-in-one" biorelevant polymers.
Author(s): Lutz, JF (Lutz, Jean-Francois); Andrieu, J (Andrieu, Julien); Uzgun, S (Uezguen, Senta); Rudolph, C (Rudolph, Carsten); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 40  Issue: 24  Pages: 8540-8543  DOI: 10.1021/ma7021474  Published: NOV 27 2007  

41) Free-radical copolymerization behavior of 5, 6-benzo-2-methylene-1, 3-dioxepane and methacrylic acid via the in-situ generation of 3-methyl-1, 5-dihydrobenzo[e] [1, 3]dioxepin-3-yl methacrylate and 2-(acetoxymethyl)benzyl methacrylate.

Author(s): Ren, LQ (Ren, Liqun); Speyerer, C (Speyerer, Christian); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 40  Issue: 22  Pages: 7834-7841  DOI: 10.1021/ma0711588  Published: OCT 30 2007  
Abstract: The copolymerization of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) with methacrylic acid (MAA) using free radical initiator like di-tert-butylperoxide resulted in different copolymer structures depending on the monomer feed ratio. The copolymerization proceeded in an unconventional way, i.e., by in situ formation of a new vinyl monomer on mixing BMDO and MAA. In this work, we found a new route to copolymerization by first adding MAA to the doul ble bond of BMDO generating a new vinyl monomer (3-methyl- 1,5-dihydrobenzo[e][1,3]dioxepin-3-yl methacrylate) with a double bond and retaining the seven membered ring of BMDO intact. The new structure is stable at 25 degrees C but underwent ring-opening at higher temperatures like 120 degrees C, generating further a different vinyl monomer with ester linkages in the side chain (2-(acetoxymethyl)benzyl methacrylate). The resulting new monomer can. copolymerize with both MAA and BMDO depending on the monomer feed ratio. The structure of the new monomers and copolymers were characterized using 1D and 2D NMR techniques.

40) Microwave assisted controlled ring-closing cyclopolymerization of diallyldimethylammonium chloride via the RAFT process.

Author(s): Assem, Y (Assem, Yasser); Greiner, A (Greiner, Andreas); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 28  Issue: 18-19  Pages: 1923-1928  DOI: 10.1002/marc.200700377  Published: SEP 18 2007  
Abstract: The present studies provide the first example of controlled free radical polymerization of a cyclopolymerizing monomer, i.e. diallyldimethylammonium chloride (DADMAC) via reversible addition fragmentation chain transfer (RAFT) chemistry in the presence of trithiocarbonate agent in aqueous solution at 60 degrees C under microwave irradiation. The polymers [poly(diallyldimethylammonium chloride), PDADMAC] were soluble in water characterization of the polymers was achieved via NMR spectroscopy. The cyclization reactions during DADMAC polymerization under microwave! irradiation attained higher conversions at each time interval as compared to thermal heating. The rate enhancements till around 520% were seen for some reactions. High molecular weight PDADMAC with narrow poly-dispersities (approaching PDI approximate to 1.05) could be made using microwave irradiation.

39) Controlled/living ring-closing cyclopolymerization of diallyldimethyl-ammonium  chloride via the RAFT process

Author(s): Assem, Y (Assem, Yasser); Chaffey-Millar, H (Chaffey-Millar, Hugh); Barner-Kowollik, C (Barner-Kowollik, Christopher); Wegner, G (Wegner, Gerhard); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULES  Volume: 40  Issue: 11  Pages: 3907-3913  DOI: 10.1021/ma0629079  Published: MAY 29 2007  
Abstract: For the first time, controlled/living free-radical polymerization of a cyclopolymerizing monomer, that is diallyldimethylammonium chloride (DADMAC), was achieved via reversible addition fragmentation chain transfer (RAFT) chemistry in the presence of both trithiocarbonate and xanthate RAFT/macromolecular design via the interchange of xanthate (MADIX) agents in aqueous solution at 60, 80, and 90 degrees C. The structural characterization of the polymers was achieved via nuclear magnetic resonance spectrometry, indicating that during the RAFT polymerization of DADMAC, identical to its equivalent conventional free radical polymerization, five-membered rings are formed almost exclusively. In the case of the trithiocarbonate agent, there was excellent agreement between the theoretical and experimental number average molecular weights, M-n, with narrow polydispersities (approaching polydispersity index (PDI) approximate to 1.10) being observed (2100 g mol(-1) < M-n < 51 000 g mol(-1)). Chain extension was carried out by sequential batchwise addition of the monomer, confirming the living character of the system. However, the increase in M-n with respect to conversion was not linear in the case of the xanthate agent, yet the PDIs were as low as 1.12, indicating that control was achieved. The inclusion of NaCl into the reaction mixture reduces of the rate of polymerization for both RAFT agents. Such an observation supports the hypothesis that electrostatic repulsion is crucial to fragmentation of the primary propagating radicals from the adduct RAFT radical; that is, it appears that an electrostatic interaction is affecting the (chemical) RAFT equilibrium.

38) Synthesis, characterization and properties evaluation of poly(N-isopropyl acrylamide-co-ester)s.

Author(s): Ren, LQ (Ren, Liqun); Agarwal, S (Agarwal, Seema)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS  Volume: 208  Issue: 3  Pages: 245-253  DOI: 10.1002/macp.200600484  Published: FEB 5 2007  
Abstract: Copolymerization behavior of cyclic ketene acetal like 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) with N-isopropylacrylamide (NIPAAm) is studied by free radical polymerization. Structural characterization is done using 1D and 2D NMR techniques. Under optimized reaction conditions, quantitative ring- opening of BMDO took place during the copolymerizations leading to the formation of poly(NIPAAm-co-ester)s. The reactivity ratios for the copolymerization of BMDO and NIPAAm were determined using Kelen-Tudos method and found to be r(BMDO) = 0.1.1. and r(NIPAAm) = 7.31. Copolymers with low mol-% of BMDO were found to be soluble in water and also showed hydrolytic degradability. Different degradable copolymers could be generated with varied glass transition temperatures and lower critical solution temperatures (LCSTs).

37) Microstructural characterisation and properties evaluation of poly (methyl methacrylate-co-ester)s.

Author(s): Agarwal, S (Agarwal, Seema)
Source: POLYMER JOURNAL  Volume: 39  Issue: 2  Pages: 163-174  DOI: 10.1295/polymj.PJ2006137  Published: 2007  
Abstract: The present work provides detailed copolymerization behavior of methyl methacrylate (MMA) with 2-methylene- 1,3-dioxepane (MDP), a cyclic ketene acetal under conventional free radical polymerization conditions at 120 degrees C. An in-sight to the microstructure of the homo- and co-polymers is also made available using I D and 2D NMR spectroscopic techniques. For the first time we showed the formation of crystalline degradable aliphatic polyester, homo poly (2-methylene-1,3-dioxepane) (PMDP) with reduced branches using radical-ring-opening-polymerisation. The copolymerization brought degradability and many other new properties to the poly (methyl methacrylate) (PMMA) vinyl polymer. Various degradable materials based on MMA and 2-methylene-1,3-dioxepane (poly (MMA-co-ester)s) containing varied amounts of ester linkages ranging from amorphous to crystalline and with different glass transition temperatures are generated. The presence of very low fraction of the ester linkages (about 10 mol %) could led to a significant increase in the thermal stability of PMMA. These materials are shown to have beat-shrinkable-shape-memory properties also.


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36) Radical ring opening and vinyl copolymerization of 2,3,4,5,6-pentafluorostyrene with 5,6-benzo-2-methylene-1,3-dioxepane: Synthesis and structural characterization using 1D and 2D NMR techniques.
Author(s): Agarwal, S (Agarwal, Seema)
Source: JOURNAL OF POLYMER RESEARCH  Volume: 13  Issue: 5  Pages: 403-412  DOI: 10.1007/s10965-006-9058-6  Published: OCT 2006  
Abstract: Radical ring opening polymerisation behaviour of 5,6-Benzo-2-methylene-1,3-dioxepane (BMDO) during its copolymerisation with 2,3,4,5,6-pentafluorostyrene (PFS) is reported using t-butyl peroxide (TBPO) conventional radical initiator. The reactivity behaviour of PFS for its copolymerisation is compared with that of the corresponding non-fluorinated monomer styrene. The presence of five fluorine atoms affected the course of polymerisation and led to the synthesis of well defined copolymers as compared to the formation of only homo poly styrene. Structural characterisation of the copolymers was done using 1D and 2D NMR spectroscopic techniques. The microstructural characterisation showed the formation of gradient copolymers with increased reaction time and/or increased amount of BMDO in the feed. The reactivity ratios for the copolymerisation of BMDO and PFS were determined using Kelen-Tudos method and was found to be r(BMDO) = 0.35 and r(PFS) = 9.9. Thermal stabilities of copolymers are also compared with that of the homopolymers.

35) Electrospinning of fluorinated polymers: formation of superhydrophobic surfaces.

Title: Electrospinning of fluorinated polymers: Formation of superhydrophobic surfaces
Author(s): Agarwal, S (Agarwal, S); Horst, S (Horst, S); Bognitzki, M (Bognitzki, M)
Source: MACROMOLECULAR MATERIALS AND ENGINEERING  Volume: 291  Issue: 6  Pages: 592-601  DOI: 10.1002/mame.200600076  Published: JUN 16 2006  
Abstract: Superhydrophobic surfaces are generated by a simple one-step method of electrospinning of fluorinated homopolymers and copolymers of PFS. The hydrophobicity and superhydrophobicity can be changed by simply changing the surface morphology, which is possible by changing the electrospinning conditions. The appropriate combination of surface morphology and fluorinated materials led to the formation of super-water-resistant coatings showing the 'water-roll' effect at an angle of 0 degrees, i.e. placement of water droplets on such surfaces was not possible as they immediately rolled away. The effect is compared with the corresponding nonfluorinated PS and found to be clearly distinct in terms of water-roll effect. Incorporation of about 30 mol-% PFS onto the PS backbone could also convert hydrophobic PS surfaces to superhydrophobic surfaces. The effect is generalized by also using a new fluorinated poly(p-xylylene) derivative. The molecular weight of the polymers has no noticeable effect on hydrophobicity/superhydrophobicity behavior.


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34) Quick atom transfer radical polymerization of N,N-diisopropyl ammonium acrylate in the presence of air.

Author(s): Kazemi, A (Kazemi, A); Agarwal, S (Agarwal, S); Greiner, A (Greiner, A)
Source: DESIGNED MONOMERS AND POLYMERS  Volume: 8  Issue: 6  Pages: 673-678  DOI: 10.1163/156855505774597731  Published: 2005  
Abstract: The atom transfer radical polymerization of N,N-diisopropyl ammonium acrylate was successfully carried out, either with continuous exposure to air or in the presence of small amounts of air, which were introduced to the reaction mixture during the polymerization. A linear growth of molecular weight as a function of conversion and low polydispersities of the polymers synthesised here were consistent with the controlled polymerization. Since the polymerization was carried out in the presence of air, oxygen may act as co-catalyst or can be an initiator in a CuBr/bipy/O-2 complex.

33) Synthesis, characterisation and properties evaluation of copolymers of 2,3,4,5,6-pentafluorostyrene and N-phenyl maleimide.

Author(s): Agarwal, S (Agarwal, S); Becker, M (Becker, M); Tewes, F (Tewes, F)
Source: POLYMER INTERNATIONAL  Volume: 54  Issue: 12  Pages: 1620-1625  DOI: 10.1002/pi.1890  Published: DEC 2005  
Abstract: Copolymers of 2,3,4,5,6-pentafluorostyrene (PFS) having a combination of high hydrophobicity and high glass transition temperature (T-g) are reported here for the first time. The copolymerization was carried out using N-phenylmaleimide (NPM) as the comonomer and azobisisobutyronitrile (AIBN) as the initiator under both conventional thermal heating and microwave heating. The initial copolymerization rate was found to be higher under microwave heating than under thermal heating. The copolymerization parameters were determined using the Fineman-Ross method and were found to be r(1) (NPM) = 0.28 and r(2) (PFS) = 0.86. Increased incorporation of NPM in the copolymers led to an increase in Tg of the copolymers without significantly affecting the hydrophobicity of poly(2,3,4,5,6-pentafluorostyrene). Thermal stability of the copolymers is also reported. (c) 2005 Society of Chemical Industry.

32) Synthesis and microstructural characterisation of copolymers of L-lactide and trimethylenecarbonate prepared using the SmI2/Sm initiator system.

Author(s): Agarwal, S (Agarwal, S); Puchner, M (Puchner, M); Greiner, A (Greiner, A); Wendorff, JH (Wendorff, JH)
Source: POLYMER INTERNATIONAL  Volume: 54  Issue: 10  Pages: 1422-1428  DOI: 10.1002/pi.1865  Published: OCT 2005  
Abstract: Polymerisation of trimethylene carbonate (TMC) and its copolymerisation with L-lactide (LA) using the SmI2/Sm initiator system is reported. The reactions were carried out at different temperatures to optimize the reaction conditions. Reactivity ratio values evaluated using the Kelen-Tiidos method were 7.24 and 0.25 for LA and TMC, respectively. Microstructure of the copolymers and its change with the reaction time is reported using 1D (H-1 and C-13) and 2D heteronuclear multiple-bond correlation NMR spectroscopic techniques. Electrospinning of the resulting copolymers was tried for the generation of fibres. Drastic deviations of the thermodynamic state from equilibrium were seen in the first heating cycle of the DSC trace of the electrospun fibres and are also reported here. (c) 2005 Society of Chemical Industry.

31) 2D NMR characterisation of 5-norbornene2-nonaneacidethylester and 5-norbornene-2-hexane.

Author(s): Mueller, K (Mueller, K); Chun, SH (Chun, SH); Greiner, A (Greiner, A); Agarwal, S (Agarwal, S)
Source: DESIGNED MONOMERS AND POLYMERS  Volume: 8  Issue: 3  Pages: 237-248  Published: 2005  
Abstract: 5-Norbornene-2-nonaneacidethylester and 5-norbomene-2-hexane were synthesised by Diels-Alder reaction of cyclopentadiene and corresponding olefins. Diels-Aider reaction usually results in a mixture of endo and exo isomers. The monomers were obtained in an approximate ratio of 75:25 (endo/exo), which was determined by GC-MS and H-1-NMR-spectroscopy. Both monomers were detailed characterized using ID H-1-NMR, ID C-13-NMR, 2D (1)HJH COSY, 2D H-1-C-13 HMQC and 2D H-1-C-13 HMBC techniques.

30) Synthesis of MMA and N-arylitaconimide block copolymers via ATRP.

Author(s): Anand, V (Anand, V); Agarwal, S (Agarwal, S); Greiner, A (Greiner, A); Choudhary, V (Choudhary, V)
Source: POLYMER INTERNATIONAL  Volume: 54  Issue: 5  Pages: 823-828  DOI: 10.1002/pi.1776  Published: MAY 2005  
Abstract: The paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N-aryl itaconimides using atom-transfer radical polymerization (ATRP) via a poly(methyl methacrylate)-Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl(3)center dot 6H(2)O/PPh3 initiating system. Poly(methyl methacrylatc) (PMMA) macroinitiator, ie with a chlorine chain-end (PMMA-Cl), having a predetermined molecular weight (M-n = 1.27 x 10(4) gmol(-1)) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl(3)center dot 6H(2)O/PPh3, which was then used to polymerize Naryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N-aryl itaconimides using the PMMA-Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N-aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N-(P-chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base-line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N-aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N-(p-chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. (c) 2005 Society of Chemical Industry.


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29) In situ formed Sm(III) catalyst from SmI2/MMA: ROP of cyclic esters.

Agarwal, S.  European Polymer Journal 2004, 40(9), 2143.



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28) Synthesis and characterization of copolymers of 5,6-benzo-2-methylene-1,3-dioxapane and styrene.

Author(s): Wickel, H (Wickel, H); Agarwal, S (Agarwal, S)
Source: MACROMOLECULES  Volume: 36  Issue: 16  Pages: 6152-6159  DOI: 10.1021/ma034551w  Published: AUG 12 2003  
Abstract: Copolymerization behavior of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) with styrene (SO is studied using benzyl bromide/CuBr/1,1,4,7,7-pentamethyldiethylenetriamine radical initiating system. Structural characterization of copolymers was done using 1D and 2D NMR techniques. The copolymer compositions were obtained from H-1 NMR spectroscopy. The reactivity ratios for the copolymerization of BMDO with St were determined using Kelen-Tudos method and was found to be r(BMDO) 1.08 and r(St) = 8.53. Degradation behavior of the copolymers is also reported.

27) SmI2/Sm-based gamma-buyrolactone-epsilon-caprolactone copolymers: Microstructural characterization using one- and two-dimensional NMR spectroscopy.

Author(s): Agarwal, S (Agarwal, S); Xie, XL (Xie, XL)
Source: MACROMOLECULES  Volume: 36  Issue: 10  Pages: 3545-3549  DOI: 10.1021/ma0258713  Published: MAY 20 2003  
Abstract: Copolymers containing nonhomopolymerizable gamma-butyrolactone (BL) and c-caprolactone (CL) units of different compositions were synthesized by the ring-opening polymerization method using the SmI2/Sm initiator system. A maximum of 33 mol % of BL was incorporated into polycaprolactone (PCL) backbone. The microstructure of these copolymers was analyzed by one- and two-dimensional NMR spectroscopies. The overlapped methylene proton signals of CL and BL were resolved using 2D H-1-C-13 heteronuclear multibond correlation (HMBC) and homonuclear H-1-H-1 total correlation spectroscopy (TOCSY) techniques. The triad sequence distribution centered at the carbonyl carbon and methylene carbon of CL and BL has been obtained from C-13 NMR spectroscopy. Further, 1D and 2D NMR spectroscopic techniques were used to confirm the change of microstructure from PCL blocks separated by discrete BL units to random copolymer structure having BL-BL units with increase in the mole percent of BL units in the copolymer.

26) Homopolymers and random copolymers of 5,6-benzo-2-methylene-1,3-dioxapane and methyl methacrylate: Structural characterization using 1D and 2D NMR.

Author(s): Wickel, H (Wickel, H); Agarwal, S (Agarwal, S); Greiner, A (Greiner, A)
Source: MACROMOLECULES  Volume: 36  Issue: 7  Pages: 2397-2403  DOI: 10.1021/ma025983u  Published: APR 8 2003  
Abstract: Complete structural characterization of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) monomer and its homopolymer is carried out using 1D and 2D NMR techniques. Copolymers of BMDO were made with MMA under ATRP reaction conditions. The copolymer compositions were obtained from H-1 NMR spectroscopy. The reactivity ratios for the copolymerization of BMDO with MMA were determined using the Kelen-Tud (o) over bars method and was found to be r(BMDO) = 0.53 and r(MMA) = 1.96. Compositional and configurational sequence analysis of copolymers is also done.

25) Samariumdiiodide based synthesis and microstructural characterization of -butyrolactone-caprolactone/lactide copolymers using one- and two-dimensional NMR spectroscopy.

Agarwal, S., Xie, X. Macromolecules 2003, 36(10), 3545.



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24) Ethylene carbonate and caprolactone copolymers: one- and two dimensional NMR characterization.

Agarwal, S., Naumann, N., Xie, X.Macromolecules 2002, 35(20), 7713.


23) Ring opening polymerizations of cyclic esters and carbonate by rare-earth LnCp3.

Author(s): Agarwal, S (Agarwal, S); Puchner, M (Puchner, M)
Source: EUROPEAN POLYMER JOURNAL  Volume: 38  Issue: 12  Pages: 2365-2371  Article Number: PII S0014-3057(02)00141-6  DOI: 10.1016/S0014-3057(02)00141-6  Published: DEC 2002  
Abstract: The ring opening polymerisation of cyclic esters (F-caprolactone and L-lactide) and cyclic carbonate (1,3-dioxan-2-one (TMC)) initiated with LnCp(3) complexes (Ln = Sm, Er, Pr, Gd and Ce) is reported. The size of the metal atom has an effect on the catalytic activity. The order of reactivity was found to be Er similar to Gd > Sm > Pr > Ce. The polyester chains were found to be living for successful synthesis of block copolymers. Polycarbonate (polyTMC) was obtained without CO2 elimination using LnCp(3) as an initiator. (C) 2002 Elsevier Science Ltd. All rights reserved.

22) Synthesis and microstructural characterization of ethylene carbonate-epsilon-caprolactone/L-lactide copolymers using one- and two-dimensional NMR spectroscopy.

Author(s): Agarwal, S (Agarwal, S); Naumann, N (Naumann, N); Xie, XL (Xie, XL)
Source: MACROMOLECULES  Volume: 35  Issue: 20  Pages: 7713-7717  DOI: 10.1021/ma020584k  Published: SEP 24 2002  
Abstract: Copolymers containing ethylene carbonate (EC) and epsilon-caprolactone (CL)/L-lactide (LA) units of different compositions were synthesized by the ring-opening polymerization method using the SmI2/Sm initiator system. EC was non-homopolymerizable using the same initiator. A maximum of 19 mol % EC was incorporated into the polycaprolactone backbone. The microstructure of these copolymers was analyzed by one- and two-dimensional NMR spectroscopies. The triad sequence distribution centered at CL has been obtained from C-13 NMR spectroscopy. 2D H-1-C-13 HMQC (heteronuclear multiple-quantum correlation) and HMBC (heteronuclear, multiple-bond correlation) spectra were used to confirm the existence of EC as isolated units and CL/LA in the blocks. The complete and correct assignment of peaks in the 13C NMR spectrum of previously reported EC-CL copolymers is also done on the basis of H-1-C-13 HMQC and HMBC spectroscopic techniques.

21) Synthesis and properties of novel poly(p-xylylene)s with aliphatic substituents

Author(s): Ishaque, M (Ishaque, M); Agarwal, S (Agarwal, S); Greiner, A (Greiner, A)
Source: E-POLYMERS  Article Number: 031  Published: JUL 3 2002  
Abstract: Poly(p-xylylene)s (PPX) with aliphatic substituents at the alpha position were synthesized by chemical vapor deposition (CVD) via vapor phase pyrolysis of alpha-chloro-1,4-xylenes, or by base-induced dehydrohalogenation of alpha-chloro-1,4-xylenes (Gilch route). These PPXs are soluble under ambient conditions in organic solvents. The glass transition temperature of the tert-butyl substituted PPX is remarkably high. Good thermal stability under nitrogen was observed for the trifluoromethyl substituted PPX. A functionalized compound suitable for polymer analogous reactions is the norbornenyl substituted PPX.

20) Diiodosamarium based polymerisations

Author(s): Agarwal, S (Agarwal, S); Greiner, A (Greiner, A)
Source: JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1  Issue: 18  Pages: 2033-2042  DOI: 10.1039/b203903f  Published: 2002  

19) SmI2 based polymerizations.

Agarwal, S., Greiner, A. J. Chem. Soc. Perkin Trans. I. 2002, 18, 2033.



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18) Sm based initiators for ring opening polymerisation of L-lactide.

Agarwal, S., Karl, M., Dehnicke, K., Greiner, A.  e-polymers 2001.



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17) Rare earth metal initiated ring opening polymerization of lactones.

Author(s): Agarwal, S (Agarwal, S); Mast, C (Mast, C); Dehnicke, K (Dehnicke, K); Greiner, A (Greiner, A)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 21  Issue: 5  Pages: 195-212  DOI: 10.1002/(SICI)1521-3927(20000301)21:5<195::AID-MARC195>3.0.CO;2-4  Published: MAR 24 2000  
Abstract: The progress in the synthesis of organolanthanide complexes supports the exploration of these compounds as initiators for ring-opening polymerization (ROP) of lactones. The performance of these initiators in terms of yield, molecular weight, polydispersity, stereoregularity is affected by the ligands and by the oxidation state of the respective rare earth metals. Several initiators are known to initiate living polymerization of lactones with excellent polydispersities of the thus obtained polymers. Differences in the performance of the initiators are caused by differences in the initiation mechanism, chain growth mechanism, or side reactions. ROP of lactones was extended to block- and graft copolymerization with polylactones, polylactides, and polyolefins either by simply utilizing living polymer chain ends, by transformation of living polymer chain ends, or by usage of polyinitiators.


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16) Sm(III) mediated graft polymerization of caprolactone and L-lactide on functionalised poly(p-xylylene)s: Model studies and polymerizations.

Author(s): Agarwal, S (Agarwal, S); Brandukova-Szmikowski, NE (Brandukova-Szmikowski, NE); Greiner, A (Greiner, A)
Source: POLYMERS FOR ADVANCED TECHNOLOGIES  Volume: 10  Issue: 9  Pages: 528-534  DOI: 10.1002/(SICI)1099-1581(199909)10:9<528::AID-PAT905>3.0.CO;2-3  Published: SEP 1999  
Abstract: The reductive coupling of ar aromatic monocarbonyl compounds in the presence of SmI2 results in the formation of Samarium(lll) dialkoxides. These Sm(III) dialkoxides have been utilized as initiators fbr ring opening polymerization (ROP) of lactones and lactides. The reductive coupling of aromatic dicarbonyl compounds results in the formation of Sm(III) polyalkoxides which have been used as polyinitiator for (ROP) of lactones and lactides. The products of this process are poly(p-xylylene)s grafted by polylactones or polylactides. Grafting efficiency depends significantly on reaction conditions and is currently limited to 28%. Copyright (C) 1999 John Wiley & Sons, Ltd.

15) Ring opening polymerization of caprolactone and valerolactone using new Sm(IIIm-halo bis(trimethylsilyl)amido complexes.

Author(s): Agarwal, S (Agarwal, S); Karl, M (Karl, M); Dehnicke, K (Dehnicke, K); Seybert, G (Seybert, G); Massa, W (Massa, W); Greiner, A (Greiner, A)
Source: JOURNAL OF APPLIED POLYMER SCIENCE  Volume: 73  Issue: 9  Pages: 1669-1674  DOI: 10.1002/(SICI)1097-4628(19990829)73:9<1669::AID-APP7>3.0.CO;2-1  Published: AUG 29 1999  
Abstract: New Sm(III) mu-halo-bis(trimethylsilyl)amido complexes [Sm(mu-X) {N(SiMe3)(2)}(2)(THF)](2) (X = Cl, Br) were synthesized and their crystal structures were analyzed. These complexes were used as catalysts for the homopolymerization of epsilon-caprolactone and delta-valerolactone and found to initiate ring-opening polymerization (ROP) of these monomers in high conversion over a short period, giving homopolymers with a moderate polydispersity index (similar to 2.0). The effect of temperature and the catalyst amount on the molecular weight distribution was also studied. Mechanistic studies were conducted using 1 : 1 and 1 : 6 molar ratios of mu-halo-bis-(trimethylsilyl)amido complexes and epsilon-caprolactone by H-1-NMR and C-13-NMR spectroscopic techniques and revealed the presence of more than one initiating species. (C) 1999 John Wiley & Sons, Inc.

14) Reactivity of Sm(II) compounds as ring opening polymerization initiators for lactones.

Author(s): Agarwal, S (Agarwal, S); Brandukova-Szmikowski, NE (Brandukova-Szmikowski, NE); Greiner, A (Greiner, A)
Source: MACROMOLECULAR RAPID COMMUNICATIONS  Volume: 20  Issue: 5  Pages: 274-278  DOI: 10.1002/(SICI)1521-3927(19990501)20:5<274::AID-MARC274>3.0.CO;2-J  Published: MAY 1999  
Abstract: Successful room temperature ring-opening polymerization (ROP) of epsilon-caprolactone and delta-valerolactone has been carried out using SmX2 (X = I, Br, and cyclopentodienyl (Cp)) catalysts. SmI2 in the presence of metallic Sm was found to have enhanced reactivity as room temperature ROP initiator for lactones as compared to pure SmI2. SmBr2 and SmCp2 showed increased reactivity compared with the Sm/SmI2 system due to their higher reductive power. The catalyst concentration and time of polymerization showed a marked effect on number-average molecular weight ((M) over bar(n)). There was a decrease in (M) over bar(n) on increasing reaction time and decreasing catalyst concentration. The initiation mechanism is discussed based on end group analysis of low molecular weight polymers.

13) Synthesis of OH-functionalised poly(p-xylylene)s by reductive coupling polymerization of aromatic dialdehydes with stoichiometric amounts of divalent Sm compounds.

Author(s): Brandukova-Szmikowski, NE (Brandukova-Szmikowski, NE); Agarwal, S (Agarwal, S); Greiner, A (Greiner, A)
Source: ACTA POLYMERICA  Volume: 50  Issue: 1  Pages: 35-39  Published: JAN 1999  
Abstract: Reductive coupling of aromatic carbonyl compounds in the presence of stoichiometric amounts of Sm(II) compounds such as SmI2, SmI2/TMSiCl, SmBr2, Sm/TMSiBr, SmCp2 resulted in hydrobenzoin derivatives. OH-functionalized poly(p-xylylene)s (OH-PPX) were obtained by reductive coupling of aromatic dialdehydes. The usage of solubilizing groups as well as the use of trimethylsilylchloride (TMSiCl) and trimethylsilylbromide (TMSiBr) enhanced the polymerizability of monomers under study. In spite of moderate yields high molecular weight polymers were obtained.

12) Kristallstrukturen der Samarium amido Komplexe [Sm(m-X)(NSiMe3)]2(THF)]2 X=Cl, Br.

Karl, M., Massa, W., Agarwal, S., Greiner, A., Dehnicke, K. Z. Anorg. Allg. Chem. 1999, 625, 1405.


11) Amidometallate von Seltenerdelementen. Synthese und Kristallstrukturen von [Na(12-Krone-4)2][M{N(SiMe3)2}3(OSiMe3)] (M = Sm, Yb), [Na(THF)3Sm{N(SiMe3)2}3(C≡C–Ph)], [Na(THF)6][Lu2(μ-NH2)(μ-NSiMe3){N(SiMe3)2}4] sowie von [NaN(SiMe3)2(THF)]2. Anwendungen der Seltenerdkomplexe als Polymerisationskatalysatoren.

Karl, M., Seybert, G., Massa, W., Agarwal, S., Greiner, A., Dehnicke, K. Z. Anorg. Allg. Chem.  1999, 625, 1301.


10) Structure property correlation in copolymers of methyl methacrylate and alkyl methacrylates.

Agarwal, S., Choudhary, V., Varma, I. K. Defence Science Journal 1999, 47(3), 401.



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9) Polysiloxanes as matrix materials for slow release of 2-pyridine aldoxime chloride. 

Gupta, D. C., Sumana, G., Agarwal, S. Polymer International 1998, 45, 211. DOI: 10.1002/(SICI)1097-0126(199802)45:2<211::AID-PI901>3.0.CO;2-F
Abstract: The efficacy of polysiloxanes and copolysiloxanes as matrix materials for the slow release of 2-pyridine aldoxime chloride (2-PAM-Cl) was investigated by in vitro studies using both slabs and microcapsules. The release rate of 2-PAM-Cl was determined in pH 7.4 phosphate buffer at 37 degrees C. Transport parameters such as the Fickian coefficient, diffusion coefficient, and the polymer-2-PAM-Cl interaction parameter were calculated. The order of release and the time taken for 80% release were also calculated. (C) 1998 SCI.


8) Determination of copper, total chromium, and silver in impregnated carbon.

Singh, B., Madhusudanan, S., Padmakumar, C. G., Sachan, S. R. S., Pandey, S. K., Agarwal, S.
Defence Science Journal 1998, 48(4), 365.
Abstract: Carbon samples were impregnated with ammonical solutions of silver salt alone and in combination with Cu and Cr salts. The impregnated samples were characterised for Cu, total Cr and Ag. Copper was extracted as CuCl2 using concentrated HCl and Cr with NaOH. Silver was extracted from impregnated carbon using HNO3 and sodium thiosulphate (Na2S2O3.5H(2)O) and ashed impregnated carbons using aqua regia. The extracted metals in their solutions were quantitatively determined by titrimetric method and atomic absorption spectroscopy. The results were within acceptable limits of error. Sodium thiosulphate is recommended for extraction of Ag, as it accomplishes complete leaching of Ag faster than the other extracting agents.



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7) Preparation and characterization of copolymers from MMA and cardanyl  methacrylate.

Agarwal, S., Choudhary, V., Varma, I. K. Die Angew. Macromol. Chemie 1997, 248 (1), 95.

DOI: 10.1002/apmc.1997.052480106
Abstract: Copolymers of methyl methacrylate (MMA) and cardanyl methacrylate (CMA) were synthesized, characterized and their physico-mechanical properties were investigated. The benzoyl peroxide-initiated copolymerization was carried out by using different mole fractions of CMA (0.02-0.10) in the initial feed at 80 degrees C. Structural characterization of copolymers was done using FTIR and H-1 NMR spectroscopic techniques. The thermal stability of the copolymers was evaluated using dynamic thermogravimetry. Incorporation of CMA in the MMA backbone leads to an improvement in thermal stability.


6) Poly(2-hydroxyethyl methacrylate) based hydrogels for slow release of Pralidoxime Chloride.

Agarwal, S., Sumana, G., Gupta, D. C. J. Appl. Polym. Sci. 1997, 66, 267.

DOI: 10.1002/(SICI)1097-4628(19971010)66:2<267::AID-APP7>3.0.CO;2-U
Abstract: Pralidoxime chloride(PAM-Cl)-loaded poly(2-hydroxyethyl methacrylate) (PHEMA)-based hydrogels were prepared by bulk copolymerization of 2-hydroxyethyl methacrylate (HEMA) with different mol fractions (0.02-0.10) of trimethylsilyl methacrylate. Characterization of the gels was done by dynamic swelling measurements. It was found that copolymerization does not alter the swelling mechanism of PHEMA. and it essentially remains Fickian in nature. In vitro drug-release studies show the increase in release time from 6 to 12 h on incorporation of a 0.1 mol fraction of trimethylsilyl methacrylate on the PHEMA backbone. (C) 1997 John Wiley & Sons, Inc.



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5) Synthesis, characterization and thermal decomposition of carbamoyl phosphonates.

Raza, S. K., Khullar, A. K., Agarwal, S. Indian Journal of Chemistry 1996, 35B, 154.
Abstract: A series of carbamoyhhosphonates (1-11) have been synthesised by the direct reaction of isocyanates with dialkyl phosphites catalysed by sodium metal. The compounds have been characterised on the basis of their analytical and spectral data Their thermal behaviour has been investigated using dynamic thermogravimetry and off-line pyrolysis gas chromatography.



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4) Measurement of diffusivities of sulphur mustard (SM) and its oxygen analog (OM) in cured butyl, nitrile and natural rubber sheets by weight gain and FT-IR-ATR methods.

Banerjee, S., Semwal, R. P., Agarwal, S. J. Appl. Polym. Sci. 1995, 57, 1483.

Abstract: The breakthrough time of butyl, nitrile, and natural-rubber sheets (cured) of different compositions against a potent chemical warfare (CW) agent have been determined using the spot disc test (SDT) method. It was observed that butyl rubber is the best material in comparison to nitrile and natural rubber for protection against sulfur mustard (SM). One of the butyl formulations provides more than 100 h protection against SM. The diffusion coefficient of oxygen mustard (SM analog) for the same formulation (F-8) and one nonblack butyl formulation (F-5) was determined by weight gain as well as by FTIR-ATR methods. Both methods provide consistent results and the diffusion coefficient of oxygen mustard (OM) for butyl rubber is in the order of 10(-9) cm(2)/s. The diffusion coefficient of SM for the formulation Fg and F, was also determined from the SDT retardation time. (C) 1995 John Wiley and Sons, Inc.



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3) Structure-property relationship in copolymers of methyl methacrylate and methacrylic acid esters Part I: Thermal behavior

Agarwal, S., Chaudhary, V., Varma, I. K. J. Appl. Polym. Sci. 1994, 53(11), 1525.

Source: JOURNAL OF APPLIED POLYMER SCIENCE  Volume: 53  Issue: 11  Pages: 1525-1531  DOI: 10.1002/app.1994.070531114  Published: SEP 12 1994  
Abstract: This article describes the synthesis and thermal characterization of copolymers of methyl methacrylate (MMA) and alkyl methacrylates. The copolymerization was carried out using different mol fractions (0.05-0.25) of alkyl methacrylates, i.e., octyl methacrylate (OMA)/decyl methacrylate (DMA)/lauryl methacrylate (LMA)/stearyl methacrylate (SMA), in the initial feed at 80-degrees-C. The copolymer composition was determined from H-1-NMR. The thermal stability of the copolymers was investigated by thermogravimetric analysis and pyrolysis gas chromatography. A two/three-step degradation was observed in the copolymer samples. The monomers were the major product of degradation in most of the copolymers except in SMA/MMA copolymers where the product of side-group elimination was also observed. An attempt was also made to determine the yield of the monomers during degradation and then to evaluate the copolymer composition. (C) 1994 John Wiley & Sons, Inc.



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2) Multifunctional epoxy resins.

Agarwal, S., Choudhary, V., Varma, I. K. J. Appl. Polym. Sci. 1993, 49, 1751.

Abstract: The curing behavior of epoxy resins prepared by reacting epichlorohydrin with 4,4'-diaminodiphenyl methane (DADPM)/4,4'-diaminodiphenyl ether (DADPE) or 4,4'-diaminodiphenyl sulfone (DDS) was investigated using DDS and tris- (m-aminophenyl) phosphine oxide (TAP) as curing agents. A broad exothermic transition with two maxima were observed in the temperature range of 100-315-degrees-C when TAP was used as the curing agent. The effect of varying DDS concentration on curing behavior of epoxy resin was also investigated. Peak exotherm temperature (T(exo)) decreased with increasing concentration of DDS, whereas heat of curing (DELTAH) increased with an increase in amine concentration up to an optimum value and then decreased. Thermal stability of the resins, cured isothermally at 200-degrees-C for 3 h, was investigated using thermogravimetric analysis in a nitrogen atmosphere. Glass fiber-reinforced multifunctional epoxy resin laminates were fabricated and the mechanical properties were evaluated. (C) 1993 John Wiley & Sons, Inc.



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1) Effect of cardanyl acrylate on thermal behavior of poly (methyl methacrylate) copolymers.

Agarwal, S., Choudhary, V., Varma, I. K. J. Appl. Polym. Sci. 1992, 46(10), 1707.

Abstract: Cardinyl acrylate (CA), prepared by the reaction of acryloyl chloride and cardinol, was copolymerized with methyl methacrylate (MMA) in bulk at 80-degrees-C using 2% benzoyl peroxide as an initiator. The copolymer composition was determined by H-1-NMR spectroscopy. Three copolymer samples containing 0.0048-0.0838 mol fraction of cardinyl acrylate were obtained. A significant improvement in the thermal stability of MMA was observed by incorporating 0.0048-0.0838 mol fraction of CA in the backbone. The activation energy for decomposition in the temperature range 350-480-degrees-C for copolymers was higher than PMMA.


Books and book chapters

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  1. Wendorff, J. H., Agarwal, S., Greiner A. Electrospinning: Materials, Processing, and Applications, (2012), Wiley.
  2. Agarwal, S. (2012) Biodegradable polyesters. In: Matyjaszewski K and Möller M (eds.) Polymer Science: A Comprehensive Reference, Vol 5, pp. 333, Amsterdam: Elsevier BV.
  3. Agarwal, S., Jin, Q., Maji, S. (2012) Biobased Polymers from Plant-Derived Tulipalin A. In: Smith, Patrick B., Gross, Richard A. (Eds)  ACS Symposium Series: Biobased monomers, polymers, and materials, Vol 1105, Chapter 13, 197-212, American Chemical Society.
  4. Agarwal, S., Greiner, A., Wendorff, J. H. (2014), Electrospinning. Kirk-Othmer Encyclopedia of Chemical Technology. DOI: 10.1002/0471238961.elecgrei.a01
  5. Agarwal S. (2015) Functional (bio)degradable polyesters by radical ring-opening polymerization. In: Stoyko Fakirov (ed.) Biodegradable polyesters, pp. 25, Wiley-VCH.
  6. Agarwal, S., Burgard, M., Greiner, A, Wendorff, J. (2016) Electrospinning: A Practical Guide to Nanofibers (De Gruyter Textbook)


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