Out of equilibrium dynamics of poly(vinyl methyl ether) segments in miscible poly(styrene)-poly(vinyl methyl ether) blends.

The local dynamics of the low-T(g) component in a polymer blend, dynamically asymmetric poly(styrene)-poly(vinyl methyl ether) (PS-PVME), is studied below the glass transition, via dielectric relaxation spectroscopy. A particular attention has been paid to blends with a high PS content (PS weight fraction higher than 50%). A relaxation process, slower than the localized motions inducing the PVME secondary relaxations, is detected. Even though these blends fall out of equilibrium in this temperature regime, the structural recovery process is not efficient on the time scale of this PVME motional process. This relaxation is attributed to rather localized, weakly cooperative PVME motions resulting from the topological constraints imposed by the frozen PS chains.