Experimental investigations of the pretransition behavior near the nematic-smectic A phase transition
Chu, Kung-Chao
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https://hdl.handle.net/2142/25614
Description
Title
Experimental investigations of the pretransition behavior near the nematic-smectic A phase transition
Author(s)
Chu, Kung-Chao
Issue Date
1977
Doctoral Committee Chair(s)
McMillan, W.L.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
pretransition behavior
nematic-smectic A phase transition
liquid crystal CBOOA
Language
en
Abstract
We present here two experiments which measure the static and dynamic pretransition behavior of the nematic-smectic A phase transition of the liquid crystal CBOOA. The first experiment is a conventional Rayleigh light scattering measurement performed with excellent temperature control of the liquid crystal. The second is a novel magneto-optic experiment which uses an external magnetic field to distort the liquid crystal and a sensitive optical interference technique to measure the distortion. Both measurements are performed with millikelvin temperature resolution and yield critical exponents for the elastic constants and the twist viscosity coefficient. These results are inconsistent with the three proposed theories of the critical behavior at least in the simple form in which the theories were first proposed and suggest that further theoretical work is necessary in order to understand this phase transition. A theory of the nonlinear elastic response of liquid crystals near the nematic-smectic A phase transition is also presented.
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