Physical aging effects on high temperature relaxations of poly(DTH carbonate) and poly(DTO carbonate) monitored by TSPC and TSDC

Thermal stimulated polarization and depolarization experiments with blocking electrodes are performed on two tyrosine-derived polycarbonates: poly(DTH carbonate) and poly(DTO carbonate). Aging effects are studied in a high temperature range that involved the contribution of the glass transition relaxation peak and the charge redistribution peak originated by the conduction through the sample and the presence of blocking electrodes. A reliable new models are used to described these high temperature relaxations and the results are presented as a function of aging times, polarization conditions and changing structure. For each sample the glass transition temperature, the parameter related with the shape of the glass transition peak and the contribution between the two modeled peaks, are found to be constant and independent of aging time. The variations in shape and temperature position of the maximum of the charge redistribution peak show logarithmic time dependence with aging time. These results are compared to the ones previously reported on a particular tyrosine-derived polyarylate, and the analysis suggests that structural differences in mobility and flexibility of the polymeric chains originate the observed variations. The examination of the experimental data indicates that charge redistribution and glass transition peaks share the same origin, and that the conduction aging effects are triggered by the onset of the glass transition.