A study of thermotropic liquid crystal systems by magnetic resonance
A study of thermotropic liquid crystal systems by magnetic resonance
This thesis is concerned with the investigation of liquid-crystalline systems using a range of techniques. The most important of these was magnetic resonance spectroscopy although optical microscopy, DSC and X-ray diffraction were also employed. Magnetic resonance spectroscopy has been used to study the orientational ordering and molecular architecture in novel systems both directly and by the use of probe molecules introduced at low concentrations. It is assumed that the probe does not perturb the structure of the host significantly. Chapter 1 gives a general introduction to liquid crystals and deuterium NMR. The following chapter presents an investigation of solute ordering in novel dimeric and monomeric crystalline systems together with their mixtures. A new model of solute ordering and the architecture of the phase in dimeric nematics is developed to account for the observed results. Chapter 3 describes an investigation of a possible nematic-nematic transition in some homologues of the 4-n-alkyloxybenzoic acids. Chapter 4 reports studies undertaken on some members from the homologous series the 4-n-alkyloxybenzylidene-4'-n-alkylanilines, the no.ms, which are an important family of mesogens exhibiting a rich polymorphism. An ESR spin probe technique is used to measure the core tilt angle in the smectic mesophases of 4-n-pentyloxybenzylidene-4'-n-pentylaniline as a function of temperature. These results are compared to the average tilt angle obtained from the layer spacings determined from an X-ray diffraction study of the pure mesogen. Chapter 5 describes an investigation of the orientational ordering and molecular architecture in the mesophases of some no.ms by deuterium NMR. Finally in chapter 6 a theory for the orientational order of rigid sub-groups for members of the homologous series of 4-n-alkyloxy-4'-cyanobiphenyls, the NOCBs, is described. The predictions based on theory are compared with the experimental results obtained from 50CB using deuterium NMR.
University of Southampton
1990
Heeks, Stephen Karl
(1990)
A study of thermotropic liquid crystal systems by magnetic resonance.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis is concerned with the investigation of liquid-crystalline systems using a range of techniques. The most important of these was magnetic resonance spectroscopy although optical microscopy, DSC and X-ray diffraction were also employed. Magnetic resonance spectroscopy has been used to study the orientational ordering and molecular architecture in novel systems both directly and by the use of probe molecules introduced at low concentrations. It is assumed that the probe does not perturb the structure of the host significantly. Chapter 1 gives a general introduction to liquid crystals and deuterium NMR. The following chapter presents an investigation of solute ordering in novel dimeric and monomeric crystalline systems together with their mixtures. A new model of solute ordering and the architecture of the phase in dimeric nematics is developed to account for the observed results. Chapter 3 describes an investigation of a possible nematic-nematic transition in some homologues of the 4-n-alkyloxybenzoic acids. Chapter 4 reports studies undertaken on some members from the homologous series the 4-n-alkyloxybenzylidene-4'-n-alkylanilines, the no.ms, which are an important family of mesogens exhibiting a rich polymorphism. An ESR spin probe technique is used to measure the core tilt angle in the smectic mesophases of 4-n-pentyloxybenzylidene-4'-n-pentylaniline as a function of temperature. These results are compared to the average tilt angle obtained from the layer spacings determined from an X-ray diffraction study of the pure mesogen. Chapter 5 describes an investigation of the orientational ordering and molecular architecture in the mesophases of some no.ms by deuterium NMR. Finally in chapter 6 a theory for the orientational order of rigid sub-groups for members of the homologous series of 4-n-alkyloxy-4'-cyanobiphenyls, the NOCBs, is described. The predictions based on theory are compared with the experimental results obtained from 50CB using deuterium NMR.
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Published date: 1990
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Local EPrints ID: 461941
URI: http://eprints.soton.ac.uk/id/eprint/461941
PURE UUID: 54591768-add1-465d-8443-244cc9c99e1c
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Date deposited: 04 Jul 2022 18:58
Last modified: 04 Jul 2022 18:58
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Author:
Stephen Karl Heeks
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