ABSTRACT
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Among the numerous new anisotropic materials studied in the past two decades, liquid crystals (LCs) and polymer composites constitute the most important segment because it is a unique class of materials that have led to the development of devices, such as privacy windows, spatial light modulators, three-dimensional displays, and large-area flat-panel displays (Doane, 1990; Broer, 1990; West, 2003). Depending on the composition of the LC and the polymer, in general, the composites with polymer as the majority of the two components are commonly described as polymer-dispersed liquid crystals (PDLCs). It has been well established that polymer morphology largely results from phase separation during polymerization. The phase separation is largely influenced by the types of matrices and LCs, concentration of the components, and the rate of temperature ramping, solvent evaporation, and gelation of
the matrix material (Drzaic, 1995). The polymers used in forming PDLCs are mostly isotropic, and universally, the reported polymer morphologies are phase-separated LC droplets encapsulated by a polymer matrix or interconnected networks. Because of high prepolymer content in the mixture, normally greater than 15% by the weight of dissolved LC, the phase separation of the polymer and the LC in PDLC systems in general, follows the spin-nodal decomposition mechanism.
