Scaling of the segmental relaxation times of polymers and its relation to the thermal expansivity

Segmental relaxation times of polymers measured at various temperatures and pressures can be superposed as a function of temperature, using a shift factor equal to the specific volume raised to a power. The material-specific scaling exponent can be linked to the nature of the intermolecular repulsive potential for the material. We show the relationship of this scaling exponent to the thermal expansivity of the material, and how it can be used to sort out the different contributions to the temperature dependence of the local dynamics.