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Studies of liquid crystalline monomers and dimers by magnetic resonance spectroscopy

Studies of liquid crystalline monomers and dimers by magnetic resonance spectroscopy
Studies of liquid crystalline monomers and dimers by magnetic resonance spectroscopy

In recent years, there has been considerable interest in the study of liquid crystalline materials not only because of their many industrial applications from high strength polymer fibres to liquid crystal electrooptic displays but also there is much interest in their fundamental behaviour. Until relatively recently, molecules which were known to exhibit liquid crystalline phases consisted of a fairly rigid core to which are attached either one or two flexible alkyl chains. However, polymeric systems exhibiting mesophases have also been discovered, the molecules of which usually consist of the same rigid units linked via flexible spacers.

Since the discovery of these semi-flexible main group liquid crystal polymers, many compounds have been synthesised which consist of just two mesogenic groups attached via a flexible spacer. These systems are known as liquid crystalline dimers and reflect the properties of polymeric systems since their structures are so similar. However, because of their simplicity they are far easier to model theoretically and due to their intriguing physical properties, are very widely studied.

This work is concerned with the synthesis and study of the physical properties of certain liquid crystalline monomers and dimers by ESR and NMR spectroscopy. The study involves measurement of the orientational order, using ESR and 2H NMR spectroscopy, and the measurement of the elastic behaviour of certain monomers and dimers by ESR spectroscopy.

Liquid crystal molecules are non-rigid and possess very little symmetry which greatly complicates their study. To overcome this, probe molecules have been used which possess some symmetry and so provides a more detailed study of these materials and their properties. We describe, where necessary, a synthesis of these materials and details of the probe molecules used.

University of Southampton
De Silva, Dinali Sharmalee
De Silva, Dinali Sharmalee

De Silva, Dinali Sharmalee (1998) Studies of liquid crystalline monomers and dimers by magnetic resonance spectroscopy. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In recent years, there has been considerable interest in the study of liquid crystalline materials not only because of their many industrial applications from high strength polymer fibres to liquid crystal electrooptic displays but also there is much interest in their fundamental behaviour. Until relatively recently, molecules which were known to exhibit liquid crystalline phases consisted of a fairly rigid core to which are attached either one or two flexible alkyl chains. However, polymeric systems exhibiting mesophases have also been discovered, the molecules of which usually consist of the same rigid units linked via flexible spacers.

Since the discovery of these semi-flexible main group liquid crystal polymers, many compounds have been synthesised which consist of just two mesogenic groups attached via a flexible spacer. These systems are known as liquid crystalline dimers and reflect the properties of polymeric systems since their structures are so similar. However, because of their simplicity they are far easier to model theoretically and due to their intriguing physical properties, are very widely studied.

This work is concerned with the synthesis and study of the physical properties of certain liquid crystalline monomers and dimers by ESR and NMR spectroscopy. The study involves measurement of the orientational order, using ESR and 2H NMR spectroscopy, and the measurement of the elastic behaviour of certain monomers and dimers by ESR spectroscopy.

Liquid crystal molecules are non-rigid and possess very little symmetry which greatly complicates their study. To overcome this, probe molecules have been used which possess some symmetry and so provides a more detailed study of these materials and their properties. We describe, where necessary, a synthesis of these materials and details of the probe molecules used.

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Published date: 1998

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Local EPrints ID: 463591
URI: http://eprints.soton.ac.uk/id/eprint/463591
PURE UUID: d87f3800-78fd-4c7e-8bdb-770c43a4f7bf

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Date deposited: 04 Jul 2022 20:54
Last modified: 04 Jul 2022 20:54

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Author: Dinali Sharmalee De Silva

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