Investigations on electric properties of polymers—II. Dielectric relaxation in atactic polystyrene determined by thermally stimulated depolarization currents

Abstract

The thermally stimulated depolarization currents (TSDC) from atactic polystyrene and d.c. conductivity of the same material have been studied over the temperature ranges 200–395 K and 363–393 K respectively. TSDC spectra are complex and consist of four peaks, β 1, β 2, β 3 (β 3 of reduced intensity) and α in order of increasing temperature. The first three peaks appeared below the glass transition temperature T g of the polymer. The β 1 peak seems to arise from a single dipolar relaxation process. The β 2 peak and probably β 3 arise from a distribution in activation energy of dipolar relaxation processes. On the basis of the molecular origin of the β relaxation process, it was suggested that β 1, β 2 and β 3 peaks involve motions of backbone chain fragments of various lengths. The last peak α appeared at T g and could be considered as a result of dipole relaxation and electric conductivity. TSDC peaks and d.c. conductivity have been related to the second order transition in the polymer.