Thermally Stimulated Depolarization Current Study on the Glass Transition of a Liquid Crystalline Copolyester

Abstract

The glass transition of a thermotropic liquid crystalline copolyester of p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) was studied by the thermally stimulated depolarization current (TSDC) technique. The poling temperature (T _p) dependence of TSDC spectra revealed the existence of another peak in the vicinity of the glass transition. This TSDC peak was considered to be the sub-T _g relaxation, distinct from the α, β and γ relaxations. It was found that the presence of the sub-T _g relaxation contributed to the apparent broadening of the glass transition of this copolyester.