Alignment behaviour and molecular dynamics of liquid crystalline side-chain polymers

Abstract

Studies made at Aberystwyth and Swansea of siloxane-chain liquid crystalline side-chain polymers (SC-LCP) provided by Professor George Gray at Hull University, together with those for certain carbon-chain SC-LCP are summarised briefly. Methods were developed to obtain materials homeotropically aligned (n||E), planarly/homogeneously aligned (n⊥E) or in any intermediate state of alignment through the use of ac electric fields of variable frequency. The molecular dynamics of the dipolar groups in these materials were studied over wide ranges of temperature and hydrostatic pressure using Broad Band Dielectric Spectroscopy covering 10⁻⁴ to 10⁵ Hz. Multiple relaxation processes were observed whose dielectric spectra changed markedly as the nature and degree of alignment were changed and the results were interpreted using macroscopic and molecular theories for the dielectric relaxation of such LCPs developed during these studies.

Keywords:

• liquid crystalline side-chain polymers
• alignment behaviour
• dielectric properties
• relaxation behaviour
• molecular dynamics

Acknowledgement

The author wishes to thank Professor John Goodby for his help in preparing the schemes for the chemical structures shown in this paper.