Internal friction and mode relaxation in a simple chain model

TL;DR

This study investigates how nonlinear interactions in a one-dimensional polymer chain model affect relaxation dynamics, revealing significant differences from harmonic chains, especially with double-well potentials modeling internal friction.

Contribution

It introduces a minimal one-dimensional model capturing internal friction effects and demonstrates how nonlinear potentials alter relaxation times and scaling behaviors.

Findings

Relaxation time of end-to-end distance can increase dramatically at intermediate temperatures.

Principal components exhibit larger relaxation times and subdiffusive scaling.

Double-well potentials significantly change relaxation properties compared to harmonic interactions.

Abstract

We consider equilibrium relaxation properties of the end-to-end distance and of principal components in a one-dimensional polymer chain model with nonlinear interaction between the beads. While for the single-well potentials these properties are similar to the ones of a Rouse chain, for the double-well interaction potentials, modeling internal friction, they differ vastly from the ones of the harmonic chain at intermediate times and intermediate temperatures. This minimal description within a one-dimensional model mimics the relaxation properties found in much more complex polymer systems. Thus, the relaxation time of the end-to-end distance may grow by orders of magnitude at intermediate temperatures. The principal components (whose directions are shown to coincide with the normal modes of the harmonic chain, whatever interaction potential is assumed) not only display larger relaxation times but also subdiffusive scaling.