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

The motion of molecular segments in poly(methylmethacrylate) (PMMA) is inve stigated in dependence on temperature and hydrostatic pressure with dielect ric and dynamic-mechanical experiments. Molecular motion can indirectly be seen in the specific volume and in the specific heat capacity. Relaxation t imes, usually plotted in activation diagrams, can be calculated by a detail ed model for the molecular structure of the polymer melt, where the free-vo lume 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 Sci ence Ltd.