Anomalous Dynamical Homogeneity of the Dielectric α-Relaxation in Miscible Polymer Blends of Poly(epichlorohydrin) and Poly(vinyl methyl ether)

The dielectric α-relaxation of the poly(epichlorohydrin)/poly(vinyl methyl ether) miscible system is investigated in the frequency range 10^-2-10⁶ 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-Watss law, the shape parameter being nearly temperature independent. This meass that the dynamical heterogeneity commonly reported for the α-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 α-relaxation range.