Influence of spacer structure on the molecular dynamics of side-chain liquid-crystalline polyacrylates as studied by dielectric relaxation spectroscopy

Abstract

The dynamic behaviour of side-chain polyacrylates, whose polymer backbones were connected to a mesogenic core composed of cyanophenyl benzoate or cyanobiphenylyl benzoate via an alkylene (C11) chain or that containing a siloxane bond as a flexible spacer chain, have been studied by dielectric relaxation spectroscopy (10²–10⁶ Hz) at different temperatures in the smectic phase. Analyses using the Fuoss–Kirkwood function, WLF equation and activation parameters on the obtained dielectric loss revealed that the siloxane-spacer apparently enhanced the mobility of a mesogenic group owing to a decrease of T_g, and that the introduction of as small a mesogen as possible might be one of the most important factors in responding rapidly to changes of an external field.