Activity Mediated Globule to Coil Transition of a Flexible Polymer in Poor Solvent

TL;DR

This study investigates how self-propulsion influences the conformational transition of a flexible polymer in poor solvent, revealing activity-driven changes in globule-coil transition dynamics and scaling behavior.

Contribution

It introduces a model incorporating activity into polymer collapse dynamics and uncovers novel scaling regimes and transition mechanisms.

Findings

Lower activity speeds up globule formation kinetics.

High activity leads to more extended polymer conformations.

Polymer transitions from globular to coil state with changing activity levels.

Abstract

Understanding the role of self-propulsion on the conformational properties of active filamentous objects has relevance in biology. In this context, we consider a flexible bead-spring model polymer for which along with both attractive and repulsive interactions among the non-bonded monomers, activity for each bead works along its intrinsic direction of self-propulsion. We study its kinetics in the overdamped limit, following a quench from good to poor solvent condition. We observe that with low activities, though the kinetic pathways remain similar, the scaling exponent for the relaxation time of globule formation becomes smaller than that for the passive case. Interestingly, for higher activities when self-propulsion dominates over interaction energy, the polymer becomes more extended. In its steady state, the variation of the spatial extension of the polymer, measured via its gyration radius, shows two completely different scaling regimes: The corresponding Flory exponent changes from $1/3$ to $3/5$ similar to a transition of the polymer from a globular state to a self-avoiding walk. This can be explained by an interplay among three energy scales present in the system, viz., the "ballistic", thermal, and interaction energy.