High strength in combination with high toughness in robust and sustainable polymeric materials
Xiaojian Liao, Martin Dulle, Juliana Martins de Souza e Silva, Ralf B. Wehrspohn, Seema Agarwal, Stephan Förster, Haoqing Hou, Paul Smith, Andreas Greiner Science, 2019, 1376-1379 DOI: 10.1126/science.aay9033
In materials science, there is an intrinsic conflict between high strength and high toughness, which can be resolved for different materials only through the use of innovative design principles. Advanced materials must be highly resistant to both deformation and fracture. We overcome this conflict in man-made polymer fibers and show multifibrillar polyacrylonitrile yarn with a toughness of 137 ± 21 joules per gram in combination with a tensile strength of 1236 ± 40 megapascals. The nearly perfect uniaxial orientation of the fibrils, annealing under tension in the presence of linking molecules, is essential for the yarn’s notable mechanical properties. This underlying principle can be used to create similar strong and tough fibers from other commodity polymers in the future and can be used in a variety of applications in areas such as biomedicine, satellite technology, textiles, aircrafts, and automobiles.
Ultralight, Soft Polymer Sponges by Self-Assembly of Short Electrospun Fibers in Colloidal Dispersions
Gaigai Duan , Shaohua Jiang , Valérie Jérôme , Joachim H. Wendorff , Amir Fathi , Jaqueline Uhm , Volker Altstädt , Markus Herling, Josef Breu , Ruth Freitag , Seema Agarwal , and Andreas Greiner, Adv. Funct. Mater. 2015, 25, 2850–2856
Ultralight polymer sponges are prepared by freeze-drying of dispersions of short electrospun fi bers. In contrast to many other highly porous materials, these sponges show extremely low densities (<3 mg cm −3 ) in combination with low specifi c 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 modifi cation of the sponges.
Functionalization of gold nanoparticles in two-phase system -via ligand exchange-
The short video shows the well-established method of ligand-exchange, which is used for the introduction of ligands to nanoparticles in one-phase and two-phase systems. Here is shown ligand exchange of citric acid ligands on gold nanoparticles against vinyl-pyridine functionalized polystyrene.