SEGMENTAL DYNAMICS HETEROGENEITY IN A MIS CIBLE 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 Spe ctroscopy. The dynamic heterogeneity observed revealed itself in a com plex pattern of the variation of heat capacity; the temperature depend ence of activation energies for segmental motion in this transition sh owed a maximum and the activation energies for segmental motion were c haracterized by significant dispersion. The dispersion of activation e nergies was attributed to the fact that the corresponding segmental mo tions involve noncooperative motions of different segments and the mot ions described by different extents of cooperativity. These motions we re identified as individual peaks in the creep rate spectra. It was de monstrated 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.