Dependence of the morphology of polymer dispersed liquid crystals on the UV polymerization process

Using confocal microscopy, we have studied the morphology of polymer dispersed liquid crystals ~PDLC! as a function of polymer/liquid crystal composition, polymer cure temperature, and ultraviolet ~UV! curing power and determined how this morphology affects the electro-optical properties. The PDLC morphology consists of a spongelike texture where spherically shaped liquid crystalline domains are dispersed in a polymer matrix. These domains grow as the fraction of liquid crystal increases and as the UV curing power decreases. We observe no significant changes in domain size with changes in the curing temperature. Instead, high-temperature cures result in coalescence and the formation of elliptical-shaped liquid crystal domains. The temperature at which this coalescence starts to be observed marks a threshold temperature T th , above which the switching properties are strongly dependent on morphology. Below T th the switching properties are largely independent of morphology. © 1997 American Institute of Physics. @S0021-8979~97!05508-4#