Effects of Alignment Activity on the Collapse Kinetics of a Flexible Polymer

TL;DR

This study investigates how active alignment interactions influence the collapse dynamics of flexible polymers, revealing faster coarsening, altered pathways, and nonmonotonic effects of activity on collapse time through molecular dynamics simulations.

Contribution

It introduces an active polymer model with alignment interactions and analyzes its collapse kinetics, highlighting differences from passive polymers and novel nonmonotonic behaviors.

Findings

Active interactions speed up coarsening process.

Collapse pathways differ from passive case, showing elongated structures.

Collapse time exhibits nonmonotonic dependence on activity strength.

Abstract

Dynamics of various biological filaments can be understood within the framework of active polymer models. Here we consider a bead-spring model for a flexible polymer chain in which the active interaction among the beads is introduced via an alignment rule adapted from the Vicsek model. Following a quench from the high-temperature coil phase to a low-temperature state point, we study the coarsening kinetics via molecular dynamics (MD) simulations using the Langevin thermostat. For the passive polymer case the low-temperature equilibrium state is a compact globule. Results from our MD simulations reveal that though the globular state is also the typical final state in the active case, the nonequilibrium pathways to arrive at such a state differ from the passive picture due to the alignment interaction among the beads. We notice that deviations from the intermediate "pearl-necklace"-like arrangement, that is observed in the passive case, and the formation of more elongated dumbbell-like structures increase with increasing activity. Furthermore, it appears that while a small active force on the beads certainly makes the coarsening process much faster, there exists nonmonotonic dependence of the collapse time on the strength of active interaction. We quantify these observations by comparing the scaling laws for the collapse time and growth of pearls with the passive case.