Induced Orientational Effects in Relaxation of Polymer Melts

TL;DR

This paper investigates how stress fluctuations in entangled polymer melts induce orientational effects in shorter chains, combining simulations and theory to explain the underlying mechanisms.

Contribution

It introduces a combined simulation and theoretical approach to explain orientational effects caused by stress fluctuations and chain screening in bi-disperse polymer melts.

Findings

Stress fluctuations are frozen on the relaxation time of longer chains.

Shorter chains are strongly oriented due to coupling with stress fluctuations.

Theoretical and simulation results agree on the mechanism of orientational coupling.

Abstract

We study stress relaxation in bi-disperse entangled polymer solutions. Shorter chains embedded in a majority of longer ones are known to be oriented by coupling to them. We analyze the mechanism for this both by computer simulation and theoretically. We show that the results can be understood in terms of stress fluctuations in a polymer melt and chain screening. Stress fluctuations are frozen on the relaxation time of the longer chains, and these will induce strong orientational couplings in the shorter chains.