Keywords

Lyotropic, Liquid crystals, Self-Assembly, Bile acid

Abstract

Liquid crystalline materials (LCMs) have gained much popularity over the past century. The thermotropic forms of these materials have been extensively studied and employed in a range of innovative applications. The lyotropic liquid crystal systems that have been studied in the past have often been formed by the organization of natural and synthetic small molecules in solutions. In this study, we use self-assembled supramolecular structures as building blocks to fabricate lyotropic liquid crystals. We investigate the self-assembly of a naturally occurring bile acid called lithocholic acid (LCA), to form supramolecular fibrous and tubular structures in basic aqueous solutions. We control the morphology of the self-assembled structures by manipulating experimental parameters in order to gain comprehensive knowledge regarding the self-assembly process. We characterize these structures with respect to their morphology i.e. their length, diameter, flexibility and shape using atomic force microscopy, optical microscopy and infrared spectroscopy. We produce lyotropic liquid crystal phases using self-assembled LCA structures through modification of physical parameters such as concentration, temperature, shear and pH. The nature of the lyotropic liquid crystal phases depends upon the morphology of the fibers and tubes. We observe that the short, rigid fibers and tubes form nematic phases while long, flexible fibers and tubes form cholesteric phases. We also study the phase transitions of the liquid crystal (LC) phases by observing their patterns using a polarizing microscope. Observations show that LC phases form in samples with LCA concentration above 0.75%w/w. Since the process of self-assembly is time-dependent, so is the formation of liquid crystal phases. We note that the optimum LCA concentration for LC phase formation is 2%-4%w/w and that the liquid crystal transition temperature is about 70[degrees]C.

Notes

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Graduation Date

2009

Advisor

Fang, Jiyu

Degree

Master of Science in Materials Science and Engineering (M.S.M.S.E.)

College

College of Engineering and Computer Science

Department

Mechanical, Materials and Aerospace Engineering

Degree Program

Materials Science & Engineering

Format

application/pdf

Identifier

CFE0002954

URL

http://purl.fcla.edu/fcla/etd/CFE0002954

Language

English

Release Date

November 2010

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

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