The effect of thermal expansion on thermally stimulated currents in polymers

Model calculations of Thermally Stimulated Polarization Currents (TSPC) based on the bistable model of Fröhlich show that the current reversals observed in the glass transition range of polymeric materials result not only from the temperature dependence of equilibrium polarization but also from the thermal expansion. The contribution of thermal expansion is especially significant in elastomers which are characterized by expansion coefficients markedly different above and below the glass transition temperature. A good qualitative and quantitative agreement with all the theoretical predictions has been found in styrene-isoprene-styrene block copolymers.