Synthesis of side-chain liquid crystal polymers by cycloplymerisation

Buxton, Ian Peter

Abstract

This project has involved the introduction of a new series of polymer backbones in the synthesis of side-chain liquid crystal (SCLC) polymers. This novel method involves the cyclopolymerisation of suitably substituted non-conjugated dienes to produce polymers incorporating allicyclic rings within the polymer backbone. The main advantage of this new methodology is that it has seldom been used to synthesise SCLC polymers in the past, so there is great scope for the production of new polymer systems.
The first main aim of this project was to optimise the polymerisation procedure, so as to maximise yields and optimise the molecular weight distribution. Once this had been done a programme of synthesis was undertaken to produce SCLC polymers which exhibited the SmC* phase, for use in display devices and for optical storage.
It was found with these new polydiene systems that some of the SCLC polymers produced wide SmC* phases, in the range » 20 to 170 °C. Unfortunately, most of the SCLC polymers produced were of low DP.
It was found that the low molecular weight was due to degradative chain transfer to monomer by abstraction of an allylic hydrogen by the growing polymer chain. As it was thought that the low DP was affecting the alignment properties of the SCLC polymers, a variety of alternative synthetic strategies were attempted to overcome this problem. The synthesis of monomers without any allylic hydrogens, in an attempt to obtain polymers of a higher molecular weight, proved to be unsuccessful. However, a polymer system was synthesised which added evidence to support the proposed structures of the polymers and the mechanism of cyclopolymerisation.
The glass transitions of the polymers occurred near to room temperature, making them potentially useful in display devices, if they exhibit the correct phases and alignment difficulties could be overcome.

Citation

Buxton, I. P. (1998). Synthesis of side-chain liquid crystal polymers by cycloplymerisation. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4223910

• Thesis Type: Thesis
• Deposit Date: Feb 9, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4223910
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Mar 1, 1998