Dielectric Spectroscopy of Side Chain Siloxane Liquid Crystal Copolymers

Side chain siloxane liquid crystal polymers (LCPs) are being investigated as potential optical storage media. Dielectric relaxation spectroscopy has been used to examine the real and imaginary components of permittivity as a function of frequency and temperature. The spectra obtained are discussed from the standpoint of both their molecular significance and their device implications. Spectra of liquid crystal homopolymers and a particular class of copolymers have been found to exhibit different features due to the larger free volume available to the mesogenic moieties in the copolymers. The relaxation behaviour of five LC copolymers is discussed and then two equivalent pairs of homopolymer and copolymer LCPs are considered in more detail. One pair shows anomalous relaxation behaviour and extra relaxation processes are attributed to internal reorientations.