Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525931
Title: Approaches to studying smectic layer elasticity and field induced deformations
Author: Siemianowski, Simon Dominik
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2010
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Abstract:
The initial aim of the work presented in this thesis was to examine smectic layer compressibility with a view to improving our understanding of the stability of intermediate phases. A natural starting point was to investigate the smectic-A phase, as it is the most basic of the smectic phases. The response of the layered structure to external fields is also a focus of this thesis as electric and magnetic fields enable the layer properties to be probed. Investigations into the reorientation dynamics of smectic-A layers in magnetic fields were performed using geometries and cell thicknesses (>50 μm) that are not feasible using electric fields. Data presented in this thesis show that three distinct reorientation mechanisms can occur, one of which is previously unreported and bridges the gap between the previously known mechanisms. The new mechanism observed in 270 μm and 340 μm thickness cells exhibits multiple stage reorientation on a timescale between tens and hundreds of seconds. Using conventional electro-optic techniques combined with a theoretical approach developed by others, this thesis presents a new technique to provide measurement of relative smectic layer compressibility of eight smectic-A liquid crystalline materials. The method presented here combines data on cell thickness, dielectric anisotropy and the measurement of the voltage threshold of the toroidal to stripe domain transition. As expected, the experimental data indicated that materials with shorter molecular lengths had the largest relative layer compressibility. Finally, direct measurement of smectic layer compressibility was investigated and the design of an apparatus capable of such measurements was undertaken. Preliminary results from such an apparatus are presented along with a discussion on the steps taken to develop the design.
Supervisor: Gleeson, Helen Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.525931  DOI: Not available
Keywords: Liquid Crystals ; x-ray diffraction
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