Dielectric relaxation and molecular motion in comb-shaped liquid crystal polymers

Abstract

Dielectric studies have been performed on a series of oriented polyacrylates in broad frequency and temperature ranges, 5 Hz to 1 GHz and – 170°C, to + 200°C respectively. In order to assist in the identification of the observed relaxation mechanisms, different molecular structures of the mesogenic pendant group connected to the main chain via a variable intermediate group have been investigated. The influence of the intermediate group (spacer length n), of the central group (O or COO), of the interphenyl group (COO) as well as that of the terminal group (CN or OCH₃), upon the nature of the relaxations (α, β, γ or ω) and the critical times of the molecular dynamics in side-chain liquid crystal polymers are discussed separately.