Component Dependence of Aggregation Structure and Light Scattering Properties of Polymer/Liquid Crystal Composite Films

Abstract

The aggregation structure and electro-optical properties of polymer/liquid crystal (LC) composite films were investigated. The aggregation structure of the composite film strongly depended on the components ratio of matrix polymer and low molecular weight liquid crystalline materials. The continuous LC phase was formed in a three dimensional polymer network when the LC weight fraction was above around 50 wt%. Also, the aggregation structure of the composite film could be controlled by controlling the solvent evaporation velocity during the film preparation process. The finer matrix polymer fibrils were formed in the case of the faster solvent evaporation velocity. The composite films exhibited reversible light scattering-light transmission switching upon electric field -OFF and -ON states, respectively. The light scattering properties of the composite film with a continuous LC phase were strongly dependent on the spatial distortion of nematic directors as well as the mismatch in refractive indices between matrix polymer and LC upon an electric field -OFF state. By controlling the polymeric wall thickness of the composite film below the wavelength (632.8 nm) of an incident He–Ne laser beam, the composite films which show a remarkably high transmittance and contrast were successfully realized.