Dynamics of a stretched nonlinear polymer chain

TL;DR

This paper investigates how nonlinear bonds affect the relaxation dynamics of stretched polymer chains using analytical models and numerical simulations, revealing mode coupling and energy transfer phenomena.

Contribution

It provides a comparative analysis of analytical and simulation methods to understand nonlinear effects in polymer relaxation dynamics under stretching.

Findings

Good agreement between GSC and Monte-Carlo at low to medium stretch

MD simulations show mode coupling and energy transfer in strongly stretched chains

Nonlinear interactions lead to a continuum of frequencies in the power spectrum

Abstract

We study the relaxation dynamics of a coarse-grained polymer chain at different degrees of stretching by both analytical means and numerical simulations. The macromolecule is modelled as a string of beads, connected by anharmonic springs, subject to a tensile force applied at the end monomer of the chain while the other end is fixed at the origin of coordinates. The impact of bond non-linearity on the relaxation dynamics of the polymer at different degrees of stretching is treated analytically within the Gaussian self-consistent approach (GSC) and then compared to simulation results derived from two different methods: Monte-Carlo (MC) and Molecular Dynamics (MD). At low and medium degrees of chain elongation we find good agreement between GSC predictions and the Monte-Carlo simulations. However, for strongly stretched chains the MD method, which takes into account inertial effects, reveals two important aspects of the nonlinear interaction between monomers: (i) a coupling and energy transfer between the damped, oscillatory normal modes of the chain, and (ii) the appearance of non-vanishing contributions of a continuum of frequencies around the characteristic modes in the power spectrum of the normal mode correlation functions.