Title page for ETD etd-042705-123130

Document Type	dissertation
Author Name	Roshi, Aleksander
Email Address	roshi at wpi.edu, sandrino01@yahoo.com
URN	etd-042705-123130
Title	Quenched Random Disorder Studies In Liquid Crystal + Aerosil Dispersions
Degree	PhD
Department	Physics
Advisors	Germano S. Iannacchione, Advisor Carl W. Garland, Committee Member Rafael Garcia, Committee Member
Keywords	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
Date of Presentation/Defense	2005-04-26
Availability	unrestricted
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.
Files	AlexRoshi-DissertationFinal.pdf

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