Segmental dynamics heterogeneity in a miscible polystyrene poly(vinyl methyl ether) blend

Segmental dynamics in a miscible polystyrene-poly(vinyl methyl ether) blend characterized by an abnormally wide glass transition region was studied using DSC and temperature laser-interferometric Creep Rate Spectroscopy. The dynamic heterogeneity observed revealed itself in a complex pattern of the variation of heat capacity; the temperature dependence of activation energies for segmental motion in this transition showed a maximum and the activation energies for segmental motion were characterized by significant dispersion. The dispersion of activation energies was attributed to the fact that the corresponding segmental motions involve noncooperative motions of different segments and the motions described by different extents of cooperativity. These motions were identified as individual peaks in the creep rate spectra. It was demonstrated that all of the observed effects could be predicted within the framework of the concept assuming common segmental origin of both alpha and beta relaxations in flexible-chain polymers.