Side chain liquid crystal polysiloxanes

Lee, Michael Siew Khay

Abstract

Laterally attached side chain liquid crystal polymers (SCLCP), which involve the appendage of the calamitic mesogenic group to the backbone via a flexible spacer in such a way that the axis of the rod-like group lies in the direction of the backbone, were first synthesised only a few years ago. As the characteristics of this new class of SCLCP are still not well defined, the preparation of laterally attached SCLCP was first examined,
so that a reliable and reproducible method could be developed to synthesise side chain homopolymers and copolymers, derived from commercially available, preformed polysiloxane backbone homopolymers and copolymers. The factors which affect the synthesis of these materials were systematically investigated, and the polymers have been fully characterised both by analytical techniques and by physical study.
The important effects of molecular weight and polydispersity of the SCLCP on phase transition temperatures are fully discussed.
Using novel mesogenic groups with an unusually asymmetric point of linkage along the molecular long axis to bond the side chain to the polymer main chain via the flexible spacer, a range of laterally attached SCLCP has been synthesised to allow the establishment of structure-property relationships. The research was geared towards the production of SCLCP that exhibit room temperature nematic phases with positive dielectric anisotropies, by the use of terminally cyano-substituted mesogenic groups, since such materials are of potential interest for speciality applications. Much effort was therefore spent on maximising the dielectric properties of the resultant polymer.
In addition, a study of side chain copolymers with terminally and laterally attached side chains has been conducted, and these mixed copolymer systems were found to offer greater control and flexibility over the fine tuning of liquid crystalline properties.

Citation

Lee, M. S. K. Side chain liquid crystal polysiloxanes. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4223936

• Thesis Type: Thesis
• Deposit Date: Feb 11, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4223936
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Sep 1, 1991