| dc.description.abstract | Lyotropic chiral nematic liquid crystalline dispersions are a unique state of matter that can be exploited to create materials with directionally dependent optical properties. Because of their unique ability to undergo a phase transition and self-assemble into a helical microstructures, chiral nematic dispersions remain a model system in which fluid phase processing can be studied. They also have great potential for industrial applications since they are capable of being processed into thin films that rotate circularly polarized light for optical sensing, security encryption, and decorative coating applications. However, many challenges remain due to complex rheological behavior and consistency in mesogen properties during preparation. In this dissertation, various aspects of processing liquid crystalline dispersions are investigated. Both external processing parameters and material parameters are explored and compared to their experimental counterparts. Confinement effects were discovered to greatly influence the orientation of the chiral microstructure in initially shear aligned dispersions. Chiral strength also altered the orientation of helical microstructures and the number of defects present in these initially shear aligned dispersions. The most uniform homeotropic helical microstructures were achieved at low chiral strength values and the tightest confinement applied by the shear apparatus.
Surface anchoring, concentration, speed of drying and chiral strength were also studied in chiral liquid crystalline dispersions as they were made into optically active thin films. For these purposes, large uniform areas of planar microstructures are desired for selective reflection applications. It was determined experimentally that biphasic dispersions formed the most uniform planar configurations when dried slowly in humid environments when placed between two anchoring surfaces. The computational work in this thesis also confirmed these results. The model was also able to show that the number of defects in the films was highly sensitive to the value of chiral strength, which generated more defects at larger values. This work serves as a basis for comparison between lab-scale experiments and their respective theoretical simulations, and paves the way for future collaborative efforts to develop thin films for practical applications. | en |
