Anomalous dynamical homogeneity of the dielectric alpha-relaxation in miscible polymer blends of poly(epichlorohydrin) and poly(vinyl methyl ether)

The dielectric alpha-relaxation of the poly(epichlorohydrin)/poly(vinyl methyl ether) miscible system is investigated in the frequency range 10(-2)-10(6) Hz. This polymer blend has the particularity that the components have nearly coincident glass-transition temperatures. We found that the relaxation spectra of these blends can be well described by the Kohlrausch-Williams-Watts law, the shape parameter being nearly temperature independent. This means that the dynamical heterogeneity commonly reported for the alpha-relaxation of miscible polymer blends is not found in this system. Our results suggest that the main reason for the dynamical homogeneity observed in the blend investigated in this work is that the neat components have nearly coincident T-g values. This can be considered as proof of the relevance of the difference between T-g of the blend components in the origin of the heterogeneous behavior commonly observed for the polymer blend dynamics in the alpha-relaxation range.