Isothermal and non-isothermal relaxation processes in dye-doped polystyrene

The buildup of a polarized state and its isothermal and nonisothermal relaxation behavior in a NLO guest-host system obtained by doping of polystyrene (PS) with the disperse red 1 (DR1) dye molecules have been studied by the isothermal absorption currents measurements, the thermally stimulated polarization (TSP) and depolarization (TSD), the AC dielectric spectroscopy, as well as the Hamon method in order to cover wide ranges of temperatures and frequencies. The 20 mu m-thick samples were poled by the "sandwich" method. Analyzing isothermal polarization and depolarization currents we proved the validity of the superposition principle. The Williams-Watts model supplemented with a concept of intrinsic time has been used to interpret the TSP curves, but it appeared that the isothermal behavior does not fully determine the TSP results. The alpha peak has been observed at dielectric loss curves with its position changing from 10 Hz at 100 degrees C to 3x10(4) Hz at 130 degrees C and narrowing with temperature. Temperature dependence of the relaxation time above T-g agreed with the Williams-Landel-Ferry model, while the Arrenius dependence was more appropriate at sub-T-g temperatures. It has been shown that the PS/DR1 system is not thermoreologically simple, i.e. the temperature-time superposition principle is not entirely valid.