The pressure and temperature dependence of the relaxation processes in poly(methylmethacrylate)

The motion of molecular segments in poly(methylmethacrylate) (PMMA) is investigated in dependence on temperature and hydrostatic pressure with dielectric and dynamic-mechanical experiments. Molecular motion can indirectly be seen in the specific volume and in the specific heat capacity. Relaxation times, usually plotted in activation diagrams, can be calculated by a detailed model for the molecular structure of the polymer melt, where the free-volume theory is replaced by the dislocation concept. The model allows us to correlate the thermal properties with the dynamic behavior, and is able to calculate specific heat capacity curves. (C) 2000 Published by Elsevier Science Ltd.