An application of thermally stimulated current technique to molecular motion analysis of polymers

Abstract

The glass transition of a liquid crystalline copolyester of p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (ANA) was studied by the thermally stimulated depolarization current (TSDC) and the thermal sampling (TS)-TSDC methods. The poling temperature (Tp) dependence of global TSDC spectra revealed the existence of the sub-Tg relaxation which was responsible for the apparent broadening of the glass transition of this copolyester. The TS-TSDC spectra also revealed that the temperature dependence of the relaxation times in both the sub-Tg and /spl alpha/ relaxations was ruled by the same compensation temperature (Tc). The physical meaning of Tc was discussed in relation to the thermal-expansion coefficient.