Control of phase-separated structure in (polymer liquid crystal) composite films and their electro-optical switching characteristics

Phase-separation behavior and electro-optical properties were investigated for the composite films consisting of the three dimensional polymer network and low molecular weight liquid crystals (LCs) embedded in the network. The composite films were prepared by a solvent cast method from uniform solutions. It was confirmed From solvent-evaporation time dependence of light scattering that the phase-separated structure of the polymer and LC components was formed via the spinodal decomposition. The resultant domain size of LC in the composite film was controlled by regulating the solvent evaporation rate. The electro-optical properties based on the electric field controlled-light scattering of the composite film was strongly dependent on the LC domain size. With increasing the LC domain size in the composite film, the rise and decay response speeds were increased and decreased, respectively, due to a decrease in an interfacial interaction between the LC and polymer phases.