Computational study of active polar polymer melts: from active reptation to activity induced local alignment

TL;DR

This study uses molecular dynamics simulations to explore how tangent polar activity influences the conformational and dynamic properties of entangled active polymer melts, revealing new behaviors and regimes.

Contribution

It introduces a comprehensive simulation analysis of active polymer melts, highlighting activity-induced conformational changes and dynamic regimes beyond existing theories.

Findings

Active reptation theory applicability range identified

Local bond alignment increases with activity

Diffusion becomes molecular-weight-independent

Abstract

This work investigates the effects of tangent polar activity on the conformational and dynamic properties of entangled polymer melts through Langevin molecular dynamics simulations. We examine systems composed of all self-propelled, monodisperse linear chains, so that constraint release is considered. The range of activities explored here includes values where the active reptation theory is applicable, as well as higher activities that challenge the validity of the theory. Chain conformations exhibit a moderate increase in coil size increase, which becomes more pronounced at higher activity levels. Under these conditions, a local bond alignment along the chain contour appears together with a non-homogeneous segmental stretching, and orientation and stretching of the tube. Dynamically, polar activity induces a molecular-weight-independent diffusion coefficient, a transient superdiffusive behavior, and an end-to-end relaxation time inversely proportional to the molecular weight. Finally, our results are summarized in a diagram that classifies the various regimes of behavior observed in the simulations. Overall, these findings provide valuable insights into the complex interplay between activity and entanglements, advancing our understanding of active polymer systems and their potential applications across various fields.