Phase Separation Kinetics of a Liquid Crystal-Polymer Mixture

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Abstract
Epoxy-based polymer-dispersed liquid crystal (PDLC) materials composed of the liquid crystal E-7, the epoxy Epon 828, and the curing agent Capcure 3–800 are formed via polymerization induced phase separation of the liquid crystal and the polymer. As the polymer reacts with the curing agent, the liquid crystal and the polymer become immiscible and the system phase separates with the liquid crystal eventually forming microdroplets in the polymer matrix. This system is interesting in that the instability of the homogeneous mixture against phase separation is brought about not by the usual temperature quench, but by polymerization of one of the components. The time evolution of the structure factor of the mixture has been studied by light scattering. We discuss the results in view of the predictions of Cahn-Hilliard theory. Liquid crystalline polymers with axial chirality are prepared. These polymers are chiral, not due to a single asymmetric carbon atom, but due to a larger molecular fragment, which is chiral as a whole. They exhibit cholesteric and chiral smectic C* phases. Dielectric spectroscopy proves strong ferroelectric properties in the chiral smectic C* phases of these polymers.