Dresden 2006 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 25: POSTER Electronic Structure and Spectroscopy

CPP 25.15: Poster

Donnerstag, 30. März 2006, 17:00–19:00, P2

Optical Switching and Dielectric Response of Nematic Liquid Crystals Dispersed in a Ferroelectric Poly(Vinylidene Fluoride/Trifluoroethylene) Matrix — •Lakshmi Meena Ganesan, Axel Mellinger, Michael Wegener, Werner Wirges, and Reimund Gerhard-Multhaupt — Department of Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam

Liquid-crystal (LC) droplets embedded in a polymer matrix induce switching behaviour in the composite film through the alignment of the director along an external electric field. When a ferroelectric material is used as host polymer, hysteretic effects in the electric-field dependence of the optical transmission occur, making these materials interesting candidates for electro-optical switches (light valves) and fundamental studies of the internal electric field in the LC cavities. Polymer-dispersed liquid-crystal (PDLC) films were prepared by dispersing a nematic liquid crystal in a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene [P(VDF-TrFE)] using a solvent-induced phase-separation method. Along with the field-dependent optical transmission of the PDLC, the hysteresis between electric displacement and electric field was measured and compared with that of the pure copolymer. As the liquid-crystal content was increased in the composite film, the coercive field was reduced, whereas the difference in transmission between the “on” and “off” state increased. In addition, the dielectric behaviour of the pure liquid crystal, of the PDLC and of the pure copolymer was measured and compared with each other.