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Novel Liquid Crystal Networks

Mork Family Department of Cheical Engineering & Material Science Presents:Rafael Verduzco
Oak Ridge National Laboratory Oak Ridge, TN"Novel Liquid Crystal Networks"AbstractThe combination of liquid crystals and polymers results in fascinating materials in which the elasticity of polymers is coupled to the liquid crystal (LC) order. In this work, we present three qualitatively different types of LC gels and elastomers and explore their electro-optical response, mechanical actuation, and flexoelectric behavior. Using block copolymer self-assembly, we prepare LC physical gels that exhibit fascinating texture transitions with temperature and multiple director relaxation modes, in contrast to covalent gels which show a single relaxation mode. Next, covalent networks with a controlled molecular weight between cross-links were prepared by "click" cross-linking of telechelic polymers produced by ring-opening metathesis polymerization. These networks swell readily in a small molecular LC solvent, 5CB, to form LC gels with high swelling ratios that exhibit a fast, reversible, and low-threshold electro-optic response. Finally, a series of bent-core liquid crystals were synthesized and used to swell calamitic monodomain liquid crystal elastomers (LCE). Nematic bent-core liquid crystals show enhanced flexoelectricity, and bent-core elastomers represent a potential method for incorporating flexoelectricity into a robust polymeric device. These LC networks and gels provide insight into the connection between physical properties and network structure and also demonstrate the broad range of materials accessible with different synthetic approaches.

Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116

Audiences: Everyone Is Invited

Contact: Petra Pearce Sapir