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

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.