A parallel algorithm for step- and chain-growth polymerization in Molecular Dynamics

TL;DR

This paper introduces a parallel algorithm for simulating step- and chain-growth polymerization within Molecular Dynamics, enabling more realistic modeling of chemical bond formation in soft-matter systems.

Contribution

It presents a novel parallel algorithm for polymerization in MD simulations, implemented in ESPResSo++, and compares its performance and results with existing tools and literature.

Findings

The algorithm produces continuous trajectories at a given intrinsic rate.

Results for chain growth align with existing simulation literature.

A rate equation for step growth matches simulation results under certain conditions.

Abstract

Classical Molecular Dynamics (MD) simulations provide insight on the properties of many soft-matter systems. In some situations it is interesting to model the creation of chemical bonds, a process that is not part of the MD framework. In this context, we propose a parallel algorithm for step- and chain-growth polymerization that is based on a generic reaction scheme, works at a given intrinsic rate and produces continuous trajectories. We present an implementation in the ESPResSo++ simulation software and compare it with the corresponding feature in LAMMPS. For chain growth, our results are compared to the existing simulation literature. For step growth, a rate equation is proposed for the evolution of the crosslinker population that compares well to the simulations for low crosslinker functionality or for short times.