Congratulation Viola to your successful defense of your Ph. D. thesis on October 20th, 2017. We wish her all the best for her future and look for to close contacts between her and us.
S. Jiang, S. Reich, B. Uch, P. Hu, S. Agarwal, A. Greiner
Appl. Mater. Interfaces 2017, 9(39), 34286-34293.
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.
S. Jiang, B. Uch, S.Agarwal, A. Greiner
ACS Appl. Mater. Interfaces, 2017, 9 (37), pp 32308–32315.
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.
G.Duan, A.Reza Bagheri, S.Jiang, J.Golenser, S.Agarwal, A. Greiner
Biomacromolecules 2017 DOI: 10.1021/acs.biomac.7b00852
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.
Our article „ Fate of So-Called Biodegradable Polymers in Seawater and Freshwater“ has been highlighted on news website AdvancedScienceNews.com.
On July 26th, 2017 Gaigai accomplished successfully the defense of her Ph. D. thesis. We sincerely congratulate her and wish all the best for a happy future.
H. Bakhshi and S. Agarwal
J. Mater. Chem. B, 2017, DOI:10.1039/C7TB01301A
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%).
M. Gernhardt, L. Peng, M. Burgard, S. Jiang, B. Förster, H. Schmalz, S. Agarwal
Macromol. Mater Eng. 2017 DOI:10.1002/mame.201700248
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.
P. Kaiser, S. Reich, D. Leykam, M. Willert-Porada, A. Greiner, R Freitag
Macromol. Biosci. 2017, 17, 1600442
Integration of electrogenic microorganisms remains a challenge in biofuel cell technology. Here, synthetic biocomposites (“artificial biofilms”) are proposed. Bacteria (Shewanella oneidensis) are embedded in a hydrogel matrix (poly(vinyl alcohol)) via wet- and electrospinning, creating fibers and nonwoven gauzes. The bacteria remain viable and metabolically active. The performance is compared to S. oneidensis suspension cultures and “natural” biofilms. While lower than with the suspension cultures, the power output from the fuel cells with the artificial biofilms is higher than with the natural one. Handling, reproducibility, and stability are also better. Artificial biofilms can therefore contribute to resolving fundamental issues of design, scale up, and monosepsis in biofuel cell technology.
A. R. Bagheri, C. Laforsch, A. Greiner, S. Agarwal
Global Challenges 2017, 1700048.
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.
New Review coauthored by Shaohua Jiang, Seema Agarwal and Andreas Greiner published in Angewandte Chemie
"Low-density open cellular sponges as functional materials''
Congratulations Amanda for successfully defending PhD work and wish you good luck for the future.
Advanced Science News highlights our work about biobased polycarbonate as BREATHING GLASS (Biobased Polycarbonate as a Gas Separation Membrane and “Breathing Glass” for Energy Saving Applications, O.Hauenstein, Md. M.Rahman, M.Elsayed, R. Krause-Rehberg, S.Agarwal, V. Abetz and A. Greiner Adv. Mater. Technol. 2017, 1700026).
For details please see:
D. Gold, M. Alian, A. Domb, Y. Karawani, M. Jbarien, J. Chollet, R. K. Haynes, H. N. Wong, V. Buchholz, A. Greiner, J. Golenser International Journal for Parasitology: Drugs and Drug Resistance, 2017, 7, 241-247.
The current treatment of schistosomiasis is based on the anti-helminthic drug praziquantel (PZQ). PZQ affects only the adult stages of schistosomes. In addition, resistance to PZQ is emerging. We suggest a drug, which could serve as a potential alternative or complement to PZQ, and as a means of treating infections at earlier, pre-granuloma stage. Derivatives of the peroxidic antimalarial drug artemisinin have been indicated as alternatives, because both plasmodia and schistosomes are blood-feeding parasites. The mechanism of action of artemisinins is related to oxidative effects of the artemisinins on intracellular reductants leading to formation of cytotoxic reactive oxygen species. We used artemisone, which has improved pharmacokinetics and anti-plasmodial activity, and reduced toxicity compared to other artemisinins in clinical use against malaria. We infected adult mice by subcutaneous injection of S. mansoni cercariae (about 200) and treated them at various times post infection by the following methods: i. artemisone suspension administered by gavage (400–450 mg/kg); ii. subcutaneous injection of a gel containing a known concentration of artemisone (115–120 mg/kg); iii. subcutaneous insertion of the drug incorporated in a solid polymer (56–60 mg/kg); iv. intraperitoneal injection of the drug solubilized in DMSO (115–120 mg/kg). Drug administration in polymers was performed to enable slow release of the artemisone that was verified in vivo and in vitro bioassays using drug-sensitive malaria parasites. We found superior strong anti-schistosome effects up to a total reduction of worm number, mainly following repetitive treatments with the drug absorbed in the polymers (73.1% and 95.9% reduction in mice treated with artemisone in gel 7 and 14, and 21, 28 and 35 days post infection, respectively). The results indicate that artemisone has a potent anti-schistosome activity. Its main importance in this context is its effectiveness in treating hosts harboring juvenile schistosomes, before egg-deposition and induction of deleterious immune responses.
K. Molnar, A. Jedlovszky-Hajdu, M. Zrinyi, S. Jiang, S. Agarwal Macromol. Rapid Commun. 2017, DOI: 10.1002/marc.201700147.
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.
A. R. Bagheri, S. Agarwal, J. Golenser, A. Greiner Global Challenges 2017,
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.
O.Hauenstein, Md. M.Rahman, M.Elsayed, R. Krause-Rehberg, S.Agarwal, V. Abetz and A. Greiner Adv. Mater. Technol. 2017, 1700026.
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.”
Tobias Moss,Ilka E. Paulus, Daniel Raps,Volker Altstädt, Andreas Greiner e-polymers, 2017, DOI: https://doi.org/10.1515/epoly-2016-0329
Particle foams and open cell sponges play nowadays an important role in academia and industrial research. The fabrication of new high-performance foams is one of the challenges. Until now, it is impossible to visualise the quality of particle foams, and the quantification is only possible with expensive analytical methods like scanning electron microscopy. In this work, we demonstrate a simple method for the visualisation of void sizes and defects inside particle foams on the basis of expanded polystyrene. The concept was transferred to porous materials, which work as templates for the formation of ultralight poly(para-xylylene) foams with stunning properties.
A.Raup, H. Wang, C.V. Synatschke, V.Jérôme, S.Agarwal, D.V. Pergushov, A. Müller and R.Freitag Biomacromolecules 2017, 18 (3), pp 808–818.
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.
S. Jiang, G. Duan, U. Kuhn, M. Mörl, V. Altstädt, A. L. Yarin, A. Greiner Angew.Chem. Int.Ed. 2017, 56,3285 –3288.
Ultralight cellular sponges offer a unique set of properties. We show here that solvent uptake by these sponges results in new gel-like materials, which we term spongy gels. The appearance of the spongy gels is very similar to classic organogels. Usually, organogels are formed by a bottom-up process. In contrast, the spongy gels are formed by a top-down approach that offers numerous advantages for the design of their properties, reproducibility, and stability. The sponges themselves represent the scaffold of a gel that could be filled with a solvent, and thereby form a mechanically stable gel-like material. The spongy gels are independent of a time-consuming or otherwise demanding in situ scaffold formation. As solvent evaporation from gels is a concern for various applications, we also studied solvent evaporation of wetting and non-wetting liquids dispersed in the sponge.
Ling Peng, Jian Zhu and Seema Agarwal Macromol. Rapid Commun. 2017, DOI: 10.1002/marc.201700034
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.
J. Golenser, V. Buchholz, A.Bagheri, A.Nasereddin, R. Dzikowski, J. Guo, N. H. Hunt, S. Eyal, N. Vakruk and A.Greiner
Parasites & Vectors, 2017, 10:117.
Cerebral malaria (CM) is a leading cause of malarial mortality resulting from infection by Plasmodium falciparum. Treatment commonly involves adjunctive care and injections or transfusion of artemisinins. All artemisinins that are in current use are metabolized to dihydroxyartemisinin (DHA), to which there is already some parasite resistance. We used artemisone, a derivative that does not convert to DHA, has improved pharmacokinetics and anti-plasmodial activity and is also anti-inflammatory (an advantage given the immunopathological nature of CM).We examined controlled artemisone release from biodegradable polymers in a mouse CM model. This would improve treatment by exposing the parasites for a longer period to a non-toxic drug concentration, high enough to eliminate the pathogen and prevent CM. The preparations were inserted into mice as prophylaxis, early or late treatment in the disease course.
The most efficient formulation was a rigid polymer, containing 80 mg/kg artemisone, which cured all of the mice when used as early treatment and 60% of the mice when used as a very late treatment (at which stage all control mice would die of CM within 24 h). In those mice that were not completely cured, relapse followed a latent period of more than seven days. Prophylactic treatment four days prior to the infection prevented CM. We also measured the amount of artemisone released from the rigid polymers using a bioassay with cultured P. falciparum. Significant amounts of artemisone were released throughout at least ten days, in line with the in vivo prophylactic results.
On February 1st, 2017 Oliver has mastered the defense of his Ph. D. thesis on biobased Polylimonenecarbonate. This topic covered aspects from synthesis, engineering, and application, which opened a new challenging research field for the chair. Thank you Oliver for your excellent work and congratulations to your great accomplishment. We wish you all the best for your next carrier step and please keep in touch.
We congratulate Paul on successfully defending his PhD work and wish him good luck for the future.
On December 2016 the members of the chair of Macromolecular Chemistry II enjoyed a very nice Christmas party as obvious from the photo taken at an early stage of the party. The party was organized by a wonderful team! Thank you very much for doing this.
Ziyin has passed her Ph. D. examination very successfully. Well done Ziyin! Her topic was on complex macromolecular architectures on metal nanoparticles, which was demanding for synthetic macromolecular chemist as well as for materials scientist. Ziyin has mastered all perfectly. We all wish her success and happiness for the future and look forward to future interaction with the people of MC II.
Hui has successfully defended her Ph. D. thesis on biodegradable and antimicrobial polymers. We wish Hui all the best for her future endeavors and challenges. Good luck and all the best Hui.
Judith Schöbel, Matthias Burgard, Christian Hils, Dr. Roland Dersch, Dr. Martin Dulle, Kirsten Volk, Prof. Dr. Matthias Karg, Prof. Dr. Andreas Greiner, Dr. Holger Schmalz
Angew. Chem. Int. Ed. 2017, 56, 405-408.
Heterogeneous catalysis with supported nanoparticles (NPs) is a highly active field of research. However, the efficient stabilization of NPs without deteriorating their catalytic activity is challenging. By combining top-down (coaxial electrospinning) and bottom-up (crystallization-driven self-assembly) approaches, we prepared patchy nonwovens with functional, nanometer-sized patches on the surface. These patches can selectively bind and efficiently stabilize gold nanoparticles (AuNPs). The use of these AuNP-loaded patchy nonwovens in the alcoholysis of dimethylphenylsilane led to full conversion under comparably mild conditions and in short reaction times. The absence of gold leaching or a slowing down of the reaction even after ten subsequent cycles manifests the excellent reusability of this catalyst system. The flexibility of the presented approach allows for easy transfer to other nonwoven supports and catalytically active NPs, which promises broad applicability.
Ilya Letnik, Ron Avrahami, Rafi Port, Andreas Greiner, Eyal Zussman, J. Stefan Rokem, Charles Greenblatt International Biodeterioration & Biodegradation, 116, (2017) 64-72.
The ability to sequester or tolerate copper has been described for a number of bacteria. It was shown that Micrococcus luteus tolerates copper, and possible mechanisms of uptake for this bacterium have been proposed. Using a count live of M. luteus (CFU), 10% survived a copper concentration of 370 ppm. Maximum sorption capacity was 59 mg of Cu2+/g of dry cells at pH 6. Several proteins of M. luteus with copper affinity were identified by enrichment on a metal-chelating resin followed by LC-MS/MS to identify the metallome. Use of SEM/EDX showed how copper concentrated on the bacterial surface, whereas TEM indicated that copper was found also inside the cells. The enhanced capability of M. luteus to bind copper was tested using three configurations: free cells on an agar surface and cells encapsulated in alginate or in electrospun polymer composites. The latter showed the highest capability to bind copper (∼76 mg Cu2+/g dry cells). Such polymer composites may potentially be used in various water-based applications such as treatment of wastewater with a high concentration of copper or other heavy metals.
Florian Käfer, Arne Lerch, Seema Agarwal
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2017, 55 (2), 274-279.
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.
Li Liu, Ali Ghaemi, Stephan Gekle, Seema Agarwal
Advanced Materials, 2016, 28 (44), 9792-9796.
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.
Benedikt R. Neugirg, Matthias Burgard, Andreas Greiner, Andreas Fery JOURNAL OF POLYMER SCIENCE, PART B: POLYMER PHYSICS, 2016, 54 (23), 2418-2424.
Design and application of mechanically extraordinary nanofibers requires their full comprehension, based on conclusive testing methods. Electrospun polymer nanofibers, for instance, show a progressive and pronounced increase in their Young's moduli when diameters decrease below the µm scale. Measurement of mechanical properties in this diameter range is challenging and in the vast majority of reports, two classes of methods are commonly used: highly sensitive tensile testing and atomic force microscopy three-point deformation testing. Despite the methods' inherent dissimilarity, we resolve their conformity for the first time, with respect to the determination of Young's moduli. Here, we benchmark them against each other for electrospun polyvinyl-alcohol nanofibers, a well-defined model system. Our results provide an experimental basis for a comprehensive understanding of nanofiber structures and its implications on their mechanical properties.
Shaohua Jiang, Haoqing Hou, Seema Agarwal and Andreas Greiner ACS Sustainable Chem. Eng., 2016 4(9), 4797-4804.
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.
Uwe Schröder, Andreas Greiner, Miriam A. Rosenbaum and Falk Harnisch Nachrichten aus der Chemie, 2016, 64(7-8), 732-737.
Die Verknüpfung von Elektrochemie und Mikrobiologie ist Forschung mit Anwendungspotenzial: von der Energiegewinnung aus Abwasser bis zur Synthese von Chemikalien. Wichtige Rollen spielen Elektrochemie, Mikrobiologie und Materialwissenschaften.
Ziyin Fan, Moritz Tebbe, Andreas Fery, Seema Agarwal and Andreas Greiner Particle & Particle Systems Characterization,2016 33(9), 698-702.
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.
Hadi Bakhshi and Seema Agarwal Polymer Chemistry,2016 7, 5322-5330.
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 °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
Viola Buchholz, Melanie Molnar, Hui Wang, Steffen Reich, Seema Agarwal, Michael Fischer, and Andreas Greiner Macromolecular Bioscience, 2016, 16(9), 1391-1397.
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.
Hui Wang, Christian Benke, Markus Hermann, Gernot Frenking and Seema Agarwal Macromolecular Chemistry and Physics,2016, 217 (16), 1834-1841.
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.
Oliver Hauenstein, Seema Agarwal, Andreas Greiner
Nature Communications, 2016, 7, Article number: 11862.
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.
Hui Wang, Markus Langner and Seema Agarwal Polymer Engineering and Science, 2016, 56(10), 1146-1152.
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.
Paul Pineda Contreras and Seema Agarwal Polym. Chem., 2016, 7, 3100-3106.
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 VCPPPG2000, 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.
New book coauthored by Seema Agarwal, Matthias Burgard, Andreas Greiner and Joachim Wendorff
Electrospinning: A Practical Guide to Nanofibers (De Gruyter Textbook)
ISBN-13: 978-3110331806 ISBN-10: 3110331802
Ultralight open cell polymer sponges with advanced properties by PPX CVD coating
Gaigai Duan, Shaohua Jiang, Tobias Moss, Seema Agarwal and Andreas Greiner Polym. Chem., 2016, 7, 2759-2764.
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.
Judith Schöbel, Matthias Karg, Dominic Rosenbach, Gert Krauss, Andreas Greiner and Holger Schmalz Macromolecules, 2016, 49(7), 2761-2771.
One-dimensional patchy nanostructures are interesting materials due to their excellent interfacial activity and their potential use as carrier for functional nanoparticles. Up to now only wormlike crystalline-core micelles (wCCMs) with a nonfunctional patchy PS/PMMA corona were accessible using crystallization-driven self-assembly (CDSA) of polystyrene-block-polyethylene-block-poly(methyl methacrylate) (SEM) triblock terpolymers. Here, we present a facile approach toward functional, patchy wCCMs, bearing tertiary amino groups in one of the surface patches. The corona forming PMMA block of a SEM triblock terpolymer was functionalized by amidation with different N,N-dialkylethylenediamines in a polymer analogous fashion. The CDSA of the functionalized triblock terpolymers in THF was found to strongly depend on the polarity/solubility of the amidated PMMA block. The lower the polarity of the amidated PMMA block (increased solubility), the higher is the accessible degree of functionalization upon which defined, well-dispersed wCCMs are formed. Interestingly, also the structure of the patchy corona can be tuned by the composition/chemistry of the functional patch, giving rise to spherical patches for R = methyl, ethyl and rectangular patches for R = isopropyl. Patchy wCCMs were successfully used as template for the selective incorporation of Au nanoparticles within the amidated corona patches, showing their potential as versatile platform for the construction of functional, mesostructured hybrid materials.
Beatriz A. Pineda-Contreras, Holger Schmalz, Seema Agarwal Polym. Chem., 2016,7, 1979-1986.
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 °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 °C influenced the thermoresponsive behavior and the chemical stability of the polymer, increasing the phase transition temperature over 30 °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 °C).
Gegenhuber, T.; Krekhova, M.; Schöbel, J.; Gröschel, A. H.; Schmalz, H. ACS Macro Letters 2016, 5(3), 306-310.
Surface-modified carbon nanotubes (CNTs) have become well-established filler materials for polymer nanocomposites. However, in immiscible polymer blends the CNT-coating is selective toward the more compatible phase, which suppresses their homogeneous distribution and limits harnessing the full potential of the filler. In this study, we show that multi-walled CNTs with a patchy polystyrene/poly(methyl methacrylate) (PS/PMMA) corona disperse equally well in both phases of an incompatible PS/PMMA polymer blend. Unlike polymer-grafted CNTs with a uniform corona, the patchy CNTs are able to adjust their corona structure to the blend phases by selective swelling/collapse of respective miscible/immiscible surface patches. Importantly, the high interfacial activity of patchy CNTs further causes a significant decrease in PMMA droplet size with increasing filler content. The combined effect of compatibilization and homogeneous distribution makes patchy CNTs interesting materials for polymer blend nanocomposites, where next to the compatibilization a homogenous filler distribution is important to gain the desired materials property (e.g. reinforcement).
Ziyin Fan, Xuelian Chen, Melissa Köhn Serrano, Holger Schmalz, Sabine Rosenfeldt,
Stephan Förster, Seema Agarwal und Andreas Greiner Angew. Chem.,2015, 127, 14747 –14752.
Eine neue, Templat-gestützte Synthese monodisperser Nanopartikel stellt keine Anforderungen an die Selbstorganisation und ist hoch reproduzierbar. Hierzu werden maßgeschneiderte Polymerkäfige für die Synthese von Nanopartikeln verwendet, die aus vernetzten Makromolekülen mit Thiolendgruppen bestehen. Goldnanopartikel (AuNPs) wurden in verschiedenen Verhältnissen von Polymerkäfig zu Gold in situ in den Polymerkäfigen synthetisiert. Die Polymerkäfige zeichneten sich dabei durch eine definierte Beladungskapazität aus, mit exzellenter Kontrolle über Form und Größe. Dagegen zeigten Kontrollversuche mit linearen Diblockcopolymeren einen linearen Anstieg der Partikelgrößen mit steigendem Goldanteil. Das unterschiedliche Wachstumsverhalten der AuNPs wird durch die Vernetzungsgrad-abhängige Flexibilität der Polymerketten erklärt. Des Weiteren wird die Polymerkäfig-gesteuerte In-situ-Synthese auf Silber- (AgNPs), Palladium- (PdNPs) und Platinnanopartikel (PtNPs) übertragen.
Joerg Bruenke, Ingolf Roschke, Seema Agarwal, Thomas Riemann and Andreas Greiner, Macromolecular Bioscience, 2016, 16(5), 647-654.
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.
Markus Langner, Andreas Greiner, Macromolecular Rapid Communications 2016, 37 (4), 351-355.
Dispersions of short electrospun fibers are utilized for the preparation of nanofiber nonwovens with different weight area on filter substrates. The aerosol filtration efficiencies of suspension-borne nanofiber nonwovens are compared to nanofiber nonwovens prepared directly by electrospinning with similar weight area. The filtration efficiencies are found to be similar for both types of nonwovens. With this, a large potential opens for processing, design, and application of new nanofiber nonwovens obtained by wet-laying of short electrospun nanofiber suspensions.
Li Liu, Shaohua Jiang, Yue Sun, and Seema Agarwal, Adv. Funct. Mater. 2016, 26(7), 1021-1027.
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.
Melissa S. Köhn Serrano, Tobias A. F. König, Johannes S. Haataja, Tina I. Löbling, Holger Schmalz, Seema Agarwal, Andreas Fery, Andreas Greiner, Macromol. Rapid Commun., 2016, 37(3), 215-220.
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.
On the occasion of a visit for the preparation of future close cooperation of macromolecular science with the Donghua University Prof. Bin Ding (on the left) and Prof. Xianfeng Wang (on the right) received the mascot of the UBT. Prof. Greiner and Prof. Agarwal were appointed by the dean of the college of engineering to visiting professors of Donghua University.
We congratulate Melissa Köhn (l) and Yinfeng Shi (r) for defending successfully their PhD work on 18th and 19th November 2015 and and wish them all the best and success in the future.
Ilka E. Paulus, Markus Heiny, V. Prasad Shastribc and Andreas Greiner Polym. Chem,. 2016, 7(1), 54-62.
Chemical vapour deposition (CVD) is a technique widely applied for the synthesis of thin and highly conformal polymer coatings. The copolymerization of poly(1,4-xylylene)s (PPX), with 2-hydroxyethyl methacrylate (HEMA) via CVD revives a hardly investigated field of PPX chemistry. The use of alkyl substituted [2.2]paracyclophanes leads to soluble PPX-copolymers. Proof of copolymerization was obtained by correlation of both monomer units in 1H,13C-HMBC 2D-NMR spectra. Next, insoluble p(PX-N-co-HEMA) copolymers were synthesized in a modified commercially available SCS Labcoater. The availability of the hydroxy ester functionality of HEMA on the film surface was indirectly confirmed by the reduction of water contact angles down to 65°. Preliminary studies using human umbilical vein endothelial cells (HUVEC) indicate the cytocompatibility of as deposited p(PX-N-co-HEMA) films.
Ilya Letnik, Ron Avrahami, J. Stefan Rokem, Andreas Greiner, Eyal Zussman, and Charles Greenblatt, Biomacromolecules, 2015, 16 (10), 3322–3328.
The preparation of composites of living functional cells and polymers is a major challenge. We have fabricated such “living composites” by preparation of polymeric microtubes that entrap yeast cells. Our approach was the process of coaxial electrospinning in which a core containing the yeast was “spun” within a shell of nonbiodegradable polymer. We utilized the yeast Candida tropicalis, which was isolated from olive water waste. It is particularly useful since it degrades phenol and other natural polyphenols, and it is capable of accumulating ethanol. The electrospun yeast cells showed significant activity of bioremediation of phenol and produced ethanol, and, in addition, the metabolic processes remained active for a prolonged period. Comparison of electrospun cells to planktonic cells showed decreased cell activity; however, the olive water waste after treatment by the yeast was no longer toxic for Escherichia coli, suggesting that detoxification and prolonged viability and activity may outweigh the reduction of efficiency.
The joint paper with the Greenblatt, Zussman, Greiner, and Rokem groups on bioremediation with yeast http://pubs.acs.org/doi/abs/10.1021/acs.biomac.5b00970 were recently discussed in an interview with Chemical Engineering News by Neil Savage which can be found under http://cen.acs.org/articles/93/web/2015/09/Yeast-Filled-Fibers-Treat-Polluted.html
O. Hauenstein, M. Reiter, S. Agarwal, B. Rieger and A. Greiner Green Chemistry, 2015 ,18, 760-770.
Completely bio-based, high molecular weight (>100 kDa) poly(limonene carbonate) (PLimC) with attractive thermal (glass transition temperature, Tg = 130 °C) and optical properties (transmission 94%, haze 0.75%) was prepared by coupling bio-based limonene oxide (LO) and carbon dioxide (CO2) using a β-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 °C could be achieved using appropriate end-capping agents. PLimC is characterised by excellent transparency and hardness.
Viola Buchholz, Seema Agarwal and Andreas Greiner Macromolecular Bioscience, 2016, 16(2), 207-213.
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
Our work on Universal Template for Controlled Size and Surface Modification of Metal Nanoparticles was presented as poster by Ziyin Fan at the Bayreuth Polymer Symposium (BPS2015) from 20th-22nd Sept. 2015. At the same conference the work on Highly Porous and Highly Conductive Metallized Polymer Sponges with Low Density by Wet Chemical Metal Deposition was presented by Markus Langer. Both contributions were judged best among the Bayreuth poster award category by the attendees. The awards were handed over by Prof. Hans-Werner Schmidt. Congratulations to the whole team working on nanoparticles and sponges and specifically to Ziyin and Markus for the international recognition and encouragement for future outstanding scientific accomplishments.
Markus Langner, Seema Agarwal, André Baudler, Uwe Schröder and Andreas Greiner Advanced Functional Materials 2015, 25(39), 6182-6188.
Exceptionally conductive (250 S cm−1), very fast electrically heatable, thermally insulating, antimicrobial 3D polymeric sponges with very low density (≈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 °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° 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.
Yinfeng Shi, Peiran Zhou, Valérie Jérôme, Ruth Freitag, and Seema Agarwal ACS Biomater. Sci. Eng., 2015, 1(10), 971-977.
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 °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.
Ling Peng, Shaohua Jiang, Maximilian Seuß, Andreas Fery, Gregor Lang, Thomas Scheibel and Seema Agarwal Macromolecular Materials and Engineering, 2016, 301(1), 48-55.
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 °C showed tensile strength 16.5 ± 1.4 MPa, modulus 205 ± 20.6 MPa, and an elongation at break of 53 ± 8%.
Florian Käfer, Fangyao Liu, Ullrich Stahlschmidt, Valérie Jérôme, Ruth Freitag, Matthias Karg, and Seema Agarwal Langmuir 2015, 31(32), 8940-89466.
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.
Peter has passed the defense of his Ph. D. thesis successfully on July 31st, 2015. He has undertaken a very successful challenge with his Ph. D. thesis and will have more challenges in the near future. We wish Peter all the best for a good future.
Paul Pineda Contreras, Christian Kuttner, Andreas Fery, Ullrich Stahlschmidt,
Valérie Jérôme, Ruth Freitag and Seema Agarwal Chem. Commun., 2015, 51, 11899-11902
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.
Martin Schieder, Thomas Lunkenbein, Carina Bojer, Martin Dulle, Julia vom Stein, Gudrun Auffermann, Tina Löbling, Judith Schöbel, Holger Schmalz and Josef Breu Z. Anorg. Allg. Chem. 2015, 641(10), 1829-1834.
We congratulate Fangyao on passing PhD examination and wish him all the best and success in the future.
Does it have to be carbon? Metal anodes in microbial fuel cells and related bioelectrochemical systems André Baudler, Igor Schmidt, Markus Langner, Andreas Greiner, Uwe Schröder Energy Environ. Sci., 2015,8, 2048-2055 DOI: 10.1039/C5EE00866B
Copper and silver are antimicrobial metals, on whose surface bacteria do not grow. As our paper demonstrates, this commonly reported antimicrobial property does not apply to electrochemically active, electrode respiring bacteria. These bacteria readily colonize the surface of these metals, forming a highly active biofilm. Average anodic current densities of 1.1 mA cm−2 (silver) and 1.5 mA cm−2 (copper) are achieved – data that are comparable to that of the benchmark material, graphite (1.0 mA cm−2). Beside the above metals, nickel, cobalt, titanium and stainless steel (SUS 304) were systematically studied towards their suitability as anode materials for microbial fuel cells and related bioelectrochemical systems. The bioelectrochemical data are put in relation to physical data of the materials (specific conductivity, standard potential) and to basic economic considerations. It is concluded that especially copper represents a highly promising anode material, suitable for application in high-performance bioelectrochemical systems.
Our work about Ultralight 3D Electrospun Nanofiber Sponge for tissue engineering was presented in Shanghai (China) on the Fiber Society’s Spring 2015 Conference in conjunction with the 2015 International Conference on Advanced Fibers and Polymer Materials, Shanghai (China) from 24th-27th May 2015 by Mrs. M.Sc. Gaigai Duan. The work was awarded with the Outstanding Poster Presentation Award Congratulations to the whole team working on ultralight sponges and specifically to Gaigai for the international recognition and encouragement for future outstanding scientific accomplishments.
Polymer/Nanoparticle Hybrid Materials of Precise Dimensions by Size-Exclusive Fishing of Metal Nanoparticles
Z. Fan, M. Köhn Serrano, A. Schaper, S. Agarwal A. Greiner
Adv. Mater.; 2015, 27(26), 3888.
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.
We congratulate Holger on passing PhD examination and wish him all the best and success in the future.
Reversible Gold Nanorod Alignment in Mechano-Responsive Elastomers
H. Pletsch, M. Tebbe, M. Dulle, B. Förster, A. Fery, S. Förster, A. Greiner, S. Agarwal
Polymer; 2015, 66, 167-172.
Highways for ions in polymers - 3D–imaging of electrochemical interphase formation
V. Wesp, J. Zakel, M. Schäfer, I. Paulus, A. Greiner, K.-M. Weitzel
Electrochim. Acta; 2015;170, 122-130.
Living composites of bacteria and polymers were utilized for sequestration of gold from aqueous hydrogen tetrachloraureate solution and for the bioconversion of nitrite.
For more details see:
Living Composites of Bacteria and Polymers as Biomimetic Films for Metal Sequestration and Bioremediation
C. Knierim, M. Enzeroth, P. Kaiser, C. Dams, D. Nette, A. Seubert, A. Klingl, C. L. Greenblatt, V. Jérôme, S. Agarwal, R. Freitag, A. Greiner
Macromol. Biosci.; 2015, 15(8), 1052-1059.
On March 15th-April 5th, Maysa Jbarien, a master student from Hebrew university of Jerusalem in Prof. Golenser’s group, visited our research labs for learning new techniques for fabrication of drug loaded nanofibrous scaffolds based on electrospinning.
Ultralight, Soft Polymer Sponges by Self-Assembly of Short Electrospun Fibers in Colloidal Dispersions
G. Duan, S. Jiang, V. Jérôme, J. H. Wendorff, A. Fathi, J. Uhm, V. Altstädt, M. Herling, J. Breu, R. Freitag, S. Agarwal, A. Greiner
Adv. Funct. Mater.; 2015; 25, 2850-2856 (pdf)
Antibacterial 45S5 Bioglass®-based scaffolds reinforced with genipin cross-linked gelatin for bone tissue engineering
W. Li, H. Wang, Y. Ding, E.C. Scheithauer, O.-M. Goudouri, A. Grünewald, R. Detsch, S. Agarwal, A. R. Boccaccini
J. Mater. Chem. B; 2015, 3(16), 3367-3378.
Synthesis of liquid crystalline thioether-functionalized hydroxypropyl cellulose esters
P. Ohlendorf, A. Greiner
Polym. Chem.; 2015, 6(14), 2734-2739.
Thermophilic films and fibers from photo cross-linkable UCST-type polymers
F. Liu, S. Jiang, L. Ionov, S. Agarwal
Polym. Chem.; 2015, 6(14), 2769-2776.
Low volume shrinkage of polymers by photopolymerization of 1,1-bis(ethoxycarbonyl)-2-vinylcyclopropanes
P. Pineda Contreras, P. Tyagia, S. Agarwal
Polym. Chem.; 2015, 6(12), 2297-2304.
Our work about UCST (upper critical solution temperature) in water and electrolytes was presented in Tsukuba (Japan) on the 10th SPSJ International Polymer Conference (IPC 2014) organized by the Society of Polymer Science, Japan (SPSJ) from 2nd - 5th Dec 2015 by Mr. Fangyao Liu. The work was highly appreciated and got the best young scientist poster award. Congratulations to the whole team working on UCST polymers and specifically to Mr. Fangyao Liu for this achievement.
Thermoresponsive Gold Nanoparticles with Positive UCST-Type Thermoresponsivity
F. Liu, S. Agarwal,
Macromol. Chem. Phys.; 2015, 216(4), 460-465.
Preparing a pseudo-solid by the reinforcement of a polydentate thioether using silver nanoparticles
H. Pletsch, A. Greiner, S. Agarwal,
Nanoscale; 2015, 7(5), 1977-1983.
Preparation of Conductive Gold Nanowires in Confined Environment of Gold-Filled Polymer Nanotubes
F. Mitschang, M. Langner, H. Vieker, A. Beyer, A. Greiner,
Macromol. Rapid Commun.; 2015, 36(3), 304-310.
One-Step Preparation of Reduction-Responsive Biodegradable Polymers as Efficient Intracellular Drug Delivery Platforms
T. Cai, Y. Cheng, Y. Wang, H. Wang, X. Liu, Q. Jin, S. Agarwal, J. Ji,
Macromol. Chem. Phys.; 2014, 215(19), 1848-1854.
Functional 2-methylene-1,3-dioxepane terpolymer: a versatile platform to construct biodegradable polymeric prodrugs for intracellular drug delivery
T. Cai, Y. Cheng, Y. Wang, H. Wang, X. Liu, Q. Jin, S. Agarwal, J. Ji,
Polym. Chem.; 2014, 5(13), 4061-4068.
Solvent-Free Aqueous Dispersions of Block Copolyesters for Electrospinning of Biodegradable Nonwoven Mats for Biomedical Applications
K. Bubel, D. Grunenberg, G. Vasilyev, E. Zussman, S. Agarwal, A. Greiner,
Macromol. Mater. Eng.; 2014; 299, 1445-1454.
Fabian has passed his defense of his Ph. D. thesis successfully on August 6th, 2014. Fabian is the first Ph. D. student of the Greiner group who defended his thesis in Bayreuth and hopefully the start of a long sequence of further defenses. We wish Fabian all the best for a good future.
Design of Soft Materials from Liquid Triblock Co-Oligomers and Metal Nanoparticles
H. Pletsch, M. J. Schnepf, S. Agarwal,
Chem. Mater.; 2014, 26(16), 4805-4811.
Shaohua Jiang has passed the defense of his Ph.D. thesis successfully on June 30th, 2014. Shaohua is the first Ph. D. student of the Agarwal group who defended his thesis in Bayreuth. Friends from Bayreuth as well as the whole MC2 group joined his examination and the after-examination party. We wish you all the best for your future.
A Non-ionic Thermophilic Hydrogel with Positive Thermosensitivity in Water and Electrolyte Solution
F. Liu, J. Seuring, S. Agarwal
Macromol. Chem. Phys.; 2014; 215, 1466-1472.
Template Assisted Change in Morphology from Particles to Nanofibers by Side-by-Side Electrospinning of Block Copolymers
S. Jiang, Q. Jin, S. Agarwal,
Macromol. Mater. Eng.; 2014, 299(11), 1298-1305.
Oligomeric dual functional antibacterial polycaprolactone
H. Wang, C. V. Synatschke, A. Raup, V. Jérôme, R. Freitag, S. Agarwal
Polym. Chem.; 2014, 5, 2453-2460.
A Rare Example of the Formation of Polystyrene-Grafted Aliphatic Polyester in One-Pot by Radical Polymerization
Y. Shi, Z. Zheng, S. Agarwal
Chem. Eur. J.; 2014, 20 (24), 7419-7428.
Highly Flexible and Tough Concentric Triaxial Polystyrene Fibers
S. Jiang, G. Duan, E. Zussman, A. Greiner, S. Agarwal,
ACS Applied Materials & Interfaces; 2014, 6(8), 5918-23.
Tea-Bag-Like Polymer Nanoreactors Filled with Gold Nanoparticles
F. Mitschang, H. Schmalz, S. Agarwal, A. Greiner,
Angew. Chem. Int. Ed.; 2014, 53, 4972–4975.
Importance of compositional homogeneity of macromolecular chains for UCST-type transitions in water: Controlled versus conventional radical polymerization
B. A. Pineda-Contreras, F. Liu, S. Agarwal,
J. Polym. Sci. Part A: Polym. Chem.; 2014, 52, 1878-1884.