Thermal Breakage and Self-Healing of a Polymer Chain under Tensile Stress

TL;DR

This study investigates the thermal breakage and self-healing behavior of polymer chains under tensile stress, combining analytical theory and molecular dynamics simulations to understand rupture mechanisms and the influence of temperature and friction.

Contribution

The paper develops a theoretical framework using Kramers-Langer theory for bond rupture and explores self-healing dynamics, validated by extensive MD simulations in 1D and 3D.

Findings

Kramers-Langer theory qualitatively describes bond rupture as a collective unstable mode.

Distribution of scission probabilities aligns with chain end effects.

Self-healing bonds increase with temperature and friction.

Abstract

We consider the thermal breakage of a tethered polymer chain of discrete segments coupled by Morse potentials under constant tensile stress. The chain dynamics at the onset of fracture is studied analytically by Kramers-Langer multidimensional theory and by extensive Molecular Dynamics simulations in 1D- and 3D-space. Comparison with simulation data in one- and three dimensions demonstrates that the Kramers-Langer theory provides good qualitative description of the process of bond-scission as caused by a {\em collective} unstable mode. We derive distributions of the probability for scission over the successive bonds along the chain which reveal the influence of chain ends on rupture in good agreement with theory. The breakage time distribution of an individual bond is found to follow an exponential law as predicted by theory. Special attention is focused on the recombination (self-healing) of broken bonds. Theoretically derived expressions for the recombination time and distance distributions comply with MD observations and indicate that the energy barrier position crossing is not a good criterion for true rupture. It is shown that the fraction of self-healing bonds increases with rising temperature and friction.