Liquid crystallinity and the role of molecular flexibility
Liquid crystallinity and the role of molecular flexibility
The work presented in this thesis examines the relationship between the structure of several new series of dimeric liquid crystals and the occurence of liquid crystalline behaviour. The alkyl spacer is shown to have a critical influence on the mesogenicity of these compounds. Chapter 1 introduces the reader to the liquid crystal phase and outlines the experimental techniques used to characterise its structure. A novel series of dimeric liquid crystals is presented in chapter 2, the α,ω-bis-(4-alkylphenylimino-benzylidene-4'-oxy)alkyldiynes. The influence of a central diacetylene unit in the alkyl spacer on liquid crystalline behaviour is highlighted.
Compared to the rich smectic polymorphism of their saturated analogues only smectic A and C behaviour is observed. In chapter 3 two series of racemic dimeric liquid crystals with branched terminal alkyl chains are reported and as expected their clearing temperatures are lower than those of their straight chain analogues. Their chiral analogues were also synthesised and in one series exhibit blue phase liquid crystalline behaviour; this is the first reported instance for dimeric systems. Chapter 4 investigates the mesogenicity of the 4-μ-alkyloxycinnamic acids when linked together or to a 4-cyanobiphenyl group via a flexible spacer. Chapter 5 investigates the symmetry of a reported biaxial nematic liquid crystal.
A deuterium NMR experiment is outlined which shows how it is possible to obtain a direct measure of the biaxiality of nematic phases exhibited by thermotropic liquid crystals. Finally, chapter 6 presents the liquid crystalline behaviour of novel disc-rod dimers when mixed with the electron acceptor TNF. In this chapter we also present results of X-ray diffraction and deuterium NMR studies of discotic dimers when mixed with varying amounts of TNF.
University of Southampton
Fletcher, Ian David
14be7eaf-91cd-49f7-91a3-6be71f828a3e
1993
Fletcher, Ian David
14be7eaf-91cd-49f7-91a3-6be71f828a3e
Fletcher, Ian David
(1993)
Liquid crystallinity and the role of molecular flexibility.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The work presented in this thesis examines the relationship between the structure of several new series of dimeric liquid crystals and the occurence of liquid crystalline behaviour. The alkyl spacer is shown to have a critical influence on the mesogenicity of these compounds. Chapter 1 introduces the reader to the liquid crystal phase and outlines the experimental techniques used to characterise its structure. A novel series of dimeric liquid crystals is presented in chapter 2, the α,ω-bis-(4-alkylphenylimino-benzylidene-4'-oxy)alkyldiynes. The influence of a central diacetylene unit in the alkyl spacer on liquid crystalline behaviour is highlighted.
Compared to the rich smectic polymorphism of their saturated analogues only smectic A and C behaviour is observed. In chapter 3 two series of racemic dimeric liquid crystals with branched terminal alkyl chains are reported and as expected their clearing temperatures are lower than those of their straight chain analogues. Their chiral analogues were also synthesised and in one series exhibit blue phase liquid crystalline behaviour; this is the first reported instance for dimeric systems. Chapter 4 investigates the mesogenicity of the 4-μ-alkyloxycinnamic acids when linked together or to a 4-cyanobiphenyl group via a flexible spacer. Chapter 5 investigates the symmetry of a reported biaxial nematic liquid crystal.
A deuterium NMR experiment is outlined which shows how it is possible to obtain a direct measure of the biaxiality of nematic phases exhibited by thermotropic liquid crystals. Finally, chapter 6 presents the liquid crystalline behaviour of novel disc-rod dimers when mixed with the electron acceptor TNF. In this chapter we also present results of X-ray diffraction and deuterium NMR studies of discotic dimers when mixed with varying amounts of TNF.
Text
405584.pdf
- Version of Record
More information
Published date: 1993
Identifiers
Local EPrints ID: 462339
URI: http://eprints.soton.ac.uk/id/eprint/462339
PURE UUID: 502f313e-0d10-4495-96ed-3879eb3684c9
Catalogue record
Date deposited: 04 Jul 2022 19:06
Last modified: 16 Mar 2024 18:55
Export record
Contributors
Author:
Ian David Fletcher
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics