Optical microscopic observation of morphology in liquid crystal/polymer composites and their electro-optical properties

We have discovered that bicyclohexyl is suitable for extracting liquid crystals from liquid crystal/polymer composites consisting of a continuous phase of nematic liquid crystal and a three-dimensional polymer network. It was confirmed in optical microscopic observation for the morphology of composites that a polymer structure, observed after extraction of liquid crystals from composites by bicyclohexyl, accorded well with the structure observed by a non-destructive method at a higher temperature than the nematic-isotropic transition point of the liquid crystal. The relationship between the polymer structure in the composite which was evaluated by the non-destructive method and the condition of phase separation induced by photo-polymerization was closely investigated from an aspect of a phase diagram and the speed of phase separation controlled by the intensity of irradiation by UV light. The electro-optical characteristics of the liquid crystal/polymer composite cells were found to be strongly affected by the polymer structure, especially the pore size of the three-dimensional network, which was especially sensitive to the intensity of UV light.