| Summary: | 博士 === 國立清華大學 === 化學工程學系 === 88 === The polymer-dispersed liquid crystal (PDLC) film was prepared from UV curable acrylic, thermal curable epoxy, and liquid crystal (LC) mixture. The UV irradiation and heat treatments were in sequential steps. In this studies, solid DICY and liquid AN2143 were respectively selected to be the curing agent for epoxy. The results showed that, for DICY system, in either thermal or polymerization-induced phase separation, the undissolved DICY particles acted as nucleation agents and were capable of inducing E63 to separate out early. Hence, the LC droplets were formed during polymerization. However, for AN2143 system, the LC droplets were not formed during polymerization but during the subsequently cooling process. A thermal stimulated current (TSC) analysis was used to investigate the physical structures of PDLC. In the TSC spectrum of PDLC, three relaxation peaks were observed: the glass transition of liquid crystal, the glass transition of polymer matrix, and the transition. The transition represents the discharge behavior of space charges, and its intensity increased as the curing time and content of the curing agent increased. The space charges would reduce the actual electrical field across the LC droplets, therefore the switching voltage of PDLC increased as the curing time and/or content of curing agent increased. In the last part of this research, we established the theoretical model to describe the light scattering behaviors of PDLC film. The model was based on the anomalous-diffraction (AD) approach and the uniform molecular orientation pattern in LC droplets was used in the model of simulation. Then, the Weibull function was adopted to define the morphologies of LC droplets in PDLC film. According to the simulation results, it could be understand that the relationship between light scattering behaviors, morphology of LC droplets, the refravtive indices of polymer matrix and molecular orientation pattern in LC droplets.
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