Electro-optical study of nematic elastomer gels

Abstract

We report on an electro-optical study of a liquid-crystal–polymer composite system. This system is made by dissolving a small amount of acrylate monomers (8%) plus crosslinkers in a nematic liquid crystal, and then photopolymerizing the homogeneous mixture. These nematic gels show properties different from those of ordinary nematics or polymer stabilized liquid crystals. By studying the electric field induced Frederiks transition, some basic properties of the nematic gels can be deduced. We compare the experimental results to a simple phenomenological model of the nematic gel, involving a characteristic length scale of order 1 $\mu$m, which is also visible as speckles, an effective internal aligning field of a few statvolts per cm, and an increased rotational viscosity on the order of ${10}^4$ P. We indicate how a microscopic model might relate the first two of these parameters.