Antiferroelectric and ferroelectric smectic C side chain liquid crystal polymers

Pringle, Steven

Abstract

Chirality in liquid crystals has been of increasing interest over the past twenty five years. More recently interesting results have been obtained in the area of chiral smectic liquid crystals with the discovery of Twist Grain Boundary (TGB), antiferroelectric and ferrielectric liquid crystal phases.
The thesis is concerned mainly with the investigation into the incidence of novel smectic phases in Side Chain Liquid Crystal Polymers (SCLCPs), and the effect structural variation has on the appearance of these phases.
A study of the effect of lateral fluoro substitution in the rigid core of the molecule on the formation of chiral smectic C phases showed how the position of the fluoro substituent affected the thermal stability of the polymeric material. This study also led to the discovery of an antiferroelectric-like structure in a polymer containing an achiral, swallow-tailed terminal chain.
The thesis also describes an "odd / even" effect when altering the length of the flexible spacer connecting the polymer backbone to the rigid core of the side chain; a polymer with a flexible spacer containing an odd number of carbon atoms exhibits an antiferroelectric phase and the corresponding analogue with an even number of carbon atoms in the flexible spacer exhibits a ferroelectric phase.
The effect of altering the moiety which connects the polymer backbone to the flexible spacer is also examined. Polymers which contain an ether functionality as the linking moiety retain their antiferroelectric properties. However, in polymers where the linking group is a "reverse ester", a smectic C phase was not observed*
The final structural feature examined in this thesis involved an examination of the effect of changing the substituent on the polymer backbone. It was found that in polymers where the linking group was an ether moiety, or a reversed ester, increasing the size and polarity of the backbone substituent did not alter the phase sequence, but the liquid crystal phase was thermally stabilised. In polymers where the backbone was linked by an ester group, markedly increasing the polarity of the backbone substituent caused the resulting SCLCP to become more glass-like; the mesophase was thermally stabilised and gave poor alignment of the side chains.

Citation

Pringle, S. Antiferroelectric and ferroelectric smectic C side chain liquid crystal polymers. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4223931

• Thesis Type: Thesis
• Deposit Date: Feb 11, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4223931
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Sep 1, 1996