Molecular dynamics simulations of active entangled polymers reptating through a passive mesh

TL;DR

This study uses molecular dynamics simulations to investigate how active forces influence the dynamics of entangled polymers, revealing that activity significantly alters chain motion without affecting their conformations.

Contribution

It introduces a novel simulation approach to study active entangled polymers and confirms theoretical predictions about their dynamic behavior under activity.

Findings

Chain conformations remain unchanged with activity.

Diffusion coefficient becomes independent of molecular weight at moderate activity.

Simulation results align with active reptation theory predictions.

Abstract

In this work, we explore the dynamics of active entangled chains using molecular dynamics simulations of a modified Kremer-Grest model. The active chains are diluted in a mesh of very long passive linear chains, to avoid constraint release effects, and an active force is applied to the monomers in a way that it imparts a constant polar drift velocity along the primitive path. The simulation results show that, over a wide range of activity values, the conformational properties of the chains and the tubes are not affected, but the dynamics of the chains are severely modified. Despite not having an explicit tube, the simulations verify all the predictions of the theory about all possible observables very accurately, including a diffusion coefficient that becomes independent of the molecular weight at moderate values of the activity. Overall, this work provides novel information on the study of active entangled polymers, giving a route map for studying this phenomenon and an efficient way of obtaining a polar activity that reproduces the physics of the active reptation theory.