Electrooptical Properties of Liquid‐Crystalline Rigid Rod‐Like Polymers with NLO‐Active Sidegroups

Abstract

AbstractThe second order nonlinear susceptibility χ(2) of a novel class of poled polymer films was investigated by means of the attenuated total reflection (ATR) method. The polymers are composed of an aromatic polyester backbone to which NLO active stilbene chromophores and flexible alkyl side chains are alternately attached. The optical properties and the dynamics of relaxation of the poled state were strongly depending on the length of the aliphatic side chains. The relaxation determined at different temperatures above and below Tg showed a temperature dependence that differs from an Arrhenius type behaviour. An empirical equation which relates the temperature dependence of the relaxation times to the glass transition temperature is presented.The polyester main chains could be macroscopically aligned in strong magnetic fields. Electric poling of the samples with aligned main chains results in ratios of χ χ which deviate significantly from the ratio of 3 one obtains for samples with isotropically distributed main chains. This behaviour is explained by the solid state structure of this kind of polymer, which is best described by a sequence of alternating layers of polyester backbones and flexible side chains.