Active polymer rings: activity-induced collapse and dynamical arrest

TL;DR

This study uses simulations to explore how activity influences the conformations of isolated active ring polymers, revealing size-dependent swelling or collapse, and identifying a universal route to these states driven by steric interactions and topology.

Contribution

It uncovers the size-dependent behavior of active ring polymers and the universal mechanisms behind their activity-induced collapse and dynamical arrest, emphasizing the role of steric interactions and topology.

Findings

Short rings swell at low activity

Longer rings collapse at high activity

Collapsed rings exhibit extremely long internal relaxation times

Abstract

We investigate, using numerical simulations, the conformations of isolated active ring polymers. We find that the their behaviour depends crucially on their size: short rings ($N \lesssim$ 100) are swelled whereas longer rings ($N \gtrsim$ 200) collapse, at sufficiently high activity. By investigating the non-equilibrium process leading to the steady state, we find a universal route driving both outcomes; we highlight the central role of steric interactions, at variance with linear chains, and of topology conservation. We further show that the collapsed rings are arrested by looking at different observables, all underlining the presence of an extremely long time scales at the steady state, associated with the internal dynamics of the collapsed section. Finally, we found that is some circumstances the collapsed state spins about its axis.