Scaling Behavior of Anisotropy Relaxation in Deformed Polymers

TL;DR

This paper introduces a new approach using small-angle neutron scattering and simulations to analyze how anisotropy relaxes in deformed polymers, revealing a unique scaling law that challenges classical models.

Contribution

It presents a novel scaling law for anisotropy relaxation in polymers, showing weak entanglement effects at microscopic scales, supported by experiments and simulations.

Findings

Relaxation rate proportional to momentum transfer Q

Scaling law valid at high Q and short times

Weak influence of entanglement on microscopic relaxation

Abstract

Drawing an analogy to the paradigm of quasi-elastic neutron scattering, we present a general approach for quantitatively investigating the spatiotemporal dependence of structural anisotropy relaxation in deformed polymers by using small-angle neutron scattering. Experiments and non-equilibrium molecular dynamics simulations on polymer melts over a wide range of molecular weights reveal that their conformational relaxation at relatively high momentum transfer $Q$ and short time can be described by a simple scaling law, with the relaxation rate proportional to $Q$. This peculiar scaling behavior, which cannot be derived from the classical Rouse and tube models, is indicative of a surprisingly weak direct influence of entanglement on the microscopic mechanism of single-chain anisotropy relaxation.