| This dissertation reports five specific experiments involving in liquid crystal and polymer composites. Before progressing onto the five experimental chapters, the first two introductory chapters cover the fundamentals of liquid crystals, such as liquid crystal phases, order, optics, electrical properties, and applications, as well as a background on liquid crystal polymer composites. First, nematic liquid crystal droplets, doped with liquid crystal monomers, adopted a twisted radial configuration. These droplets were suspended in silicone oil and were subjected to applied electric fields as well as temperature changes before and after polymerization. Second, a nematic liquid crystal exhibited a frozen polarization when a polymer network was present inside the liquid crystal bulk and a strong DC field was applied to the liquid crystal during polymerization. Polymer concentration and DC field strength during curing were varied in order to find the relationship between these variables and polarization effect. Finally, a dielectric study was conducted on these polymer stabilized liquid crystal samples before and after curing. Third, a polymer network was introduced inside a vertical alignment (VA) mode liquid crystal display to reduce the turn-off switching time. The turn-off time as well as contrast ratio was observed in polymer stabilized VA mode displays as the polymer concentration and rubbings along substrate alignment layer were varied. Light scattering studies on these displays and an independent study on reverse mode polymer stabilized liquid crystal displays were also performed and discussed. Fourth, a polymer-stabilized reflective cholesteric liquid crystal displays were created. These displays, consisting of a nematic liquid crystal with chiral dopants and monomers, were light reflecting at zero field, and the liquid crystal helical director was stabilized by the polymer network. When a field was applied and increased, the reflection band shifted from the initial state. The degree of shifting was observed and from that, we were able to get a picture on how the liquid crystal director responded to the increasing fields when held by the polymer network. Fifth, microstructures of different sizes and shapes were imprinted on liquid crystal elastomer films. Two lithography techniques were used in creating these structures and the structures were compared by using a polarizing microscope and scanning electron microscopy. Also the structures were studied when heated and cooled. Finally, a concluding chapter summarizes results from the experimental chapters and the future of liquid crystal polymer composites was also explored in the closing chapter. |
