Electrically and Thermally Switchable Selective Bragg Reflection in Cholesteric Liquid Crystalline Composite Films

Abstract

In order to explore the effect of temperature and electric field on the reflective band of cholesteric liquid crystalline composite films, a novel chiral monomer, (-)-cholesteryl 4-(6-acryloyloxyhexyloxy) phenyl-4'-phenyl carbonate, was synthesized. The corresponding cholesteric composite films were prepared upon photopolymerization. Thermally and electrically switched blue-shifts of the selective light reflection of cholesteric films are observed. The bandwidth of the broadened reflective band can be enhanced by blending two individual cholesteric composite films after thermal annealing and diffusion was also investigated. The color of the cholesteric composite film can be tuned. The whole visible range is accessible by varying the film temperature or the voltage. Such materials could be beneficial for manufacturing optical films e.g. color filters, cholesteric reflective polarizers, and brightness enhancement films.