The Electro -Optical Dynamics of Nanoscale Liquid Crystalline Mesophases
Lee, Lay Min
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https://hdl.handle.net/2142/84213
Description
Title
The Electro -Optical Dynamics of Nanoscale Liquid Crystalline Mesophases
Author(s)
Lee, Lay Min
Issue Date
2005
Doctoral Committee Chair(s)
Nuzzo, Ralph G.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
The surface-dependent anchoring and electro-optical (EO) dynamics of thin liquid crystalline (LC) films of 4-n-pentyl-4'-cyanobiphenyl (5CB) have been examined using polarized Fourier-transform infrared (FTIR) and step-scan time-resolved (TRS) vibrational spectroscopies. A simple coarse-grained statistical dynamical model was presented to provide both qualitative and quantitative understandings of these behaviors. In the experiments detailed in this work, new strategies for controlling the anchoring interactions were explored; namely, the alignments that were induced by a polyimide layer and those that are imparted by a substrate presenting nanometer-scaled corrugations. The influences of temperature on the anchoring and EO dynamics of the nematic mesophase in a LC system whose surface anchoring effects were well characterized are also examined. The dynamical behaviors of the system were seen to be mediated by the temperature-dependence of the elastic constants and the viscosity of the LC medium and serve to confirm the predictions of theory. Using similar alignment protocols, a novel twisted organization of the nematic mesophase was produced, in which the molecular director of the LC film undergoes a 90° twist. This mesoscopic organization engenders significant impacts on the EO dynamics as compared to more conventional planar alignments and can be exploited as a design principle to effectively influence the electric field-induced dynamics of LC systems.
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