Compensation law in several polymer relaxations

It is well known that there is a compensation law between the change of enthalpy and change of entropy associated with the relaxations of several polymers. We have already suggested that the temperatures of transition from one relaxation to another correspond to a thermodynamic transition. In this paper, we show that the slope of the compensation law is the inverse of the transition temperatures of various polymers (PVC, PTFE, PP, PS, etc.). It is also shown that within the transition temperatures range, the relaxations of the studied polymers are single relaxation time processes. In other words, there is no need for complex (and often unexplained) distribution of relaxation times. It is often suggested that dielectric and mechanical relaxation measurements give similar information on the studied relaxations. A detailed analysis of the Gibbs free activation energy of several results indicate that this is not entirely true. The activation energy (not to be confused with the so-called energy of activation deduced from Arrhenius plots) of the dielectric measurements are systematically lower than those deduced from mechanical measurements.