Morphology of polymer-stabilized liquid crystals

The morphology of liquid crystal/polymer composite systems developed for potential applications in flat-panel displays has been studied in detail. Composites were prepared by free-radical polymerization of a dilute solution of a tetrafunctional monomer in a liquid-crystal solvent. The growth mechanism for the morphology was observed and the effect of flexible spacers in the mesogenic monomers on the morphology has been studied, The initial polymer micronetwork formed by these tetrafunctional cross-linkable monomers grows to a critical molecular weight and/or branch content and phase separates from its low-molar-mass liquid-crystal solvent. The internal structure of these beadlike structures depends strongly on the flexible spacers and the temperature of polymerization. As the reaction proceeds, the beads aggregate initially by a reaction limited mechanism, and they continue to expel the liquid-crystal solvent as the cross-link density increases, The final diffusion-limited morphology ranges from a disorderly collection of nearly isotropic beads to a highly oriented fibrillar network. The interaction between the final polymer network and the liquid-crystal solvent is also markedly different.