The University of Southampton
University of Southampton Institutional Repository

New liquid crystals for display mixtures

New liquid crystals for display mixtures
New liquid crystals for display mixtures
This thesis is concerned with the design, synthesis and properties of thermotropic liquid crystals based on the fluorene and 9,10-dihydrophenanthrene core units. Derivatives of 9,10-dihydrophenathrene were found to be both expensive to prepare and difficult to purify, and attention was concentrated on fluorene derivatives. Simple 2,7-disubstituted fluorenes are either monotropic or exhibit enantiotropic smectic phases. Accordingly a third benzene ring was directly coupled to the fluorene core to give a 2-phenylfluorene. The homologous series of 2-(4-cyanophenyl)-7-alkylfluorenes from ethyl to nonyl was prepared via a five step convergent synthesis, and the compounds were isolated as white crystalline solids. All the compounds exhibited enantiotropic nematic phases, and the heptyl, octyl and nonyl homologues also exhibited a smectic A phase. The parent compound 2-(4 cyanophenyl)fluorene with no alkyl chain was prepared by a similar route, but did not exhibit an enantiotropic mesophase. Some physical properties of 2-(4-cyanophenyl)-7-pentylfluorene were measured, and many values {e.g. dielectric anisotropy and birefringence) were similar to those for the commercially successful 4-pentyl-4" -cyano-p-terphenyl. However 2-phenylfluorene material had a higher viscosity. These properties could be related to the crescent shape of the 2-phenylfluorene core, which is dictated by the bridging methylene group. Lateral substitution of the fluorene core was investigated in an attempt to prepare low melting point derivatives. Four C9 alkylated compounds were prepared, and these were found to be oils. However no mesophases were detected. Some 2-(4 alkoxyphenyl)-7-alkylfluorenes were prepared as low birefringence analogues, but these were found to exhibit smectic phases at high temperatures. The analogous alkoxy compound 2-pentoxy-7-(4 cyanophenyl)fluorene was prepared but could not be satisfactorily purified. Preliminary investigations into partial reduction of the fluorene core were carried out, but these did not progress beyond an early stage.
University of Southampton
Boardman, Frederick H.
81bca963-70ee-44ee-9d30-db9e7b65bcb9
Boardman, Frederick H.
81bca963-70ee-44ee-9d30-db9e7b65bcb9
Grossel, Martin
403bf3ff-6364-44e9-ab46-52d84c6f0d56

Boardman, Frederick H. (2001) New liquid crystals for display mixtures. University of Southampton, Doctoral Thesis, 244pp.

Record type: Thesis (Doctoral)

Abstract

This thesis is concerned with the design, synthesis and properties of thermotropic liquid crystals based on the fluorene and 9,10-dihydrophenanthrene core units. Derivatives of 9,10-dihydrophenathrene were found to be both expensive to prepare and difficult to purify, and attention was concentrated on fluorene derivatives. Simple 2,7-disubstituted fluorenes are either monotropic or exhibit enantiotropic smectic phases. Accordingly a third benzene ring was directly coupled to the fluorene core to give a 2-phenylfluorene. The homologous series of 2-(4-cyanophenyl)-7-alkylfluorenes from ethyl to nonyl was prepared via a five step convergent synthesis, and the compounds were isolated as white crystalline solids. All the compounds exhibited enantiotropic nematic phases, and the heptyl, octyl and nonyl homologues also exhibited a smectic A phase. The parent compound 2-(4 cyanophenyl)fluorene with no alkyl chain was prepared by a similar route, but did not exhibit an enantiotropic mesophase. Some physical properties of 2-(4-cyanophenyl)-7-pentylfluorene were measured, and many values {e.g. dielectric anisotropy and birefringence) were similar to those for the commercially successful 4-pentyl-4" -cyano-p-terphenyl. However 2-phenylfluorene material had a higher viscosity. These properties could be related to the crescent shape of the 2-phenylfluorene core, which is dictated by the bridging methylene group. Lateral substitution of the fluorene core was investigated in an attempt to prepare low melting point derivatives. Four C9 alkylated compounds were prepared, and these were found to be oils. However no mesophases were detected. Some 2-(4 alkoxyphenyl)-7-alkylfluorenes were prepared as low birefringence analogues, but these were found to exhibit smectic phases at high temperatures. The analogous alkoxy compound 2-pentoxy-7-(4 cyanophenyl)fluorene was prepared but could not be satisfactorily purified. Preliminary investigations into partial reduction of the fluorene core were carried out, but these did not progress beyond an early stage.

Text
Boardman - Version of Record
Available under License University of Southampton Thesis Licence.
Download (17MB)

More information

Published date: 1 March 2001

Identifiers

Local EPrints ID: 427017
URI: http://eprints.soton.ac.uk/id/eprint/427017
PURE UUID: 4da1a6e0-76c0-4bf3-808d-b3fc9f9955c0
ORCID for Martin Grossel: ORCID iD orcid.org/0000-0001-7469-6854

Catalogue record

Date deposited: 20 Dec 2018 17:30
Last modified: 27 Mar 2020 01:24

Export record

Contributors

Author: Frederick H. Boardman
Thesis advisor: Martin Grossel ORCID iD

University divisions

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

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×