Is there a higher-order Mode Coupling transition in polymer blends?

Abstract

We present simulations on a binary blend of bead-spring polymer chains. The introduction of monomer size disparity yields very different relaxation times for each component of the blend. Competition between two different arrest mechanisms, namely bulk-like dynamics and confinement, leads to an anomalous relaxation scenario for the fast component, characterized by sublinear time dependence for mean squared displacements, or logarithmic decay and convex-to-concave crossover for density-density correlators. These anomalous dynamic features, which are observed over time intervals extending up to four decades, strongly resemble predictions of Mode Coupling Theory for nearby higher-order transitions. Chain connectivity extends anomalous relaxation over a wide range of blend compositions.