Thermally stimulated polarization (TSPC) and depolarization currents (TSDC) are measured on polyethylene terephthalate (PET) copolymerized with p-hydroxy benzoic acid (PHB). These systems are important since they comprise components of many commercial polymer liquid crystals (PLCs). There has been some speculation about the origins of the multiple transition peaks in TSDC of PLCs and secondary peaks have frequently been designated as resulting from Maxwell-Wagner interphase polarization. The applicability of this designation for main chain PLCs has been investigated. TSDC as a function of field strength and window polarization has been conducted and the transitions have been identified as glass transition peaks as opposed to space charge relaxations. A comparison of the TSDC current versus the polarization current (TSPC) reveals that TSPC is not generated for transitions associated with the PHB component.