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

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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.