Faculty Advisor or Committee Member

Germano S. Iannacchione, Advisor

Faculty Advisor or Committee Member

Carl W. Garland, Committee Member

Faculty Advisor or Committee Member

Rafael Garcia, Committee Member

Identifier

etd-042705-123130

Abstract

This thesis presents a series of studies of quenched random disorder (QRD) on liquid crystals. We have used high-resolution AC-Calorimetry, high-resolution X-Ray Diffraction (XRD), X-Ray Intensity Fluctuation Spectroscopy (XIFS), Turbidity, Integrated Low-Angle Light Scattering (ILALS), as well as Polarizing Microscopy to characterize the effects of a nano-colloidal dispersions of aerosils in the phase transitions of several liquid crystals. The aerosil ($SIL$) is made of 70~AA~ diameter SiO$_{2}$ particles coated with hydroxyl (-OH) groups. The coating allows the $SIL$ particles to hydrogen-bond together, to form a very low density gel in an organic solvent. This provides the quenched random disorder. The liquid crystals of interest are: octyloxycyanobiphenyl ($8OCB$), 4-extit{n}-pentylphenylthiol-4'-extit{n}-octyloxybenzoate (ar{8}$S5), 4'-transbutyl-4-cyano-4-heptyl-bicyclohexane ($CCN47$), and octylcyanobiphenyl ($8CB$). Studies have been carried out as a function of aerosil concentration and temperature spanning the following phase transitions, Isotropic to Nematic (emph{I-N}), nematic to smectic-emph{A} (emph{N-SmA}), smectic-emph{A} to smectic-emph{C} (emph{SmA-SmC}), and crystallization.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Physics

Project Type

Dissertation

Date Accepted

2005-04-27

Accessibility

Unrestricted

Subjects

smectic-A to smectic-C, nematic to smectic-A, isotropic-nematic, phase transition, quenched random disorder, liquid crystal, gel structure, turbidity, gel dynamics, x-ray intensity fluctuation spectroscopy ( XIFS ), ac-calorimetry, x-ray difraction, Liquid crystals, Silica, Phase transformations (Statistical physics)

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