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

TL;DR

This study uses simulations to explore complex relaxation behaviors in polymer blends with size disparity, revealing features akin to higher-order Mode Coupling Theory transitions.

Contribution

It demonstrates that chain connectivity and component competition induce anomalous relaxation phenomena similar to higher-order MCT transitions in polymer blends.

Findings

Anomalous relaxation features such as sublinear MSD and logarithmic decay.

Crossover from convex to concave density correlators.

Anomalous dynamics persist across various blend compositions.

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.