Unfolding of a diblock chain and its anomalous diffusion induced by active particles

TL;DR

This study investigates how active particles influence the structural unfolding and anomalous diffusion of a diblock copolymer chain, revealing new mechanisms for controlling polymer behavior using active matter.

Contribution

It introduces a detailed simulation of diblock copolymer dynamics in active particle baths, uncovering novel unfolding patterns and diffusion behaviors induced by activity.

Findings

Unfolding pattern resembles woolen string extraction.

Critical force decreases then plateaus with increasing B block length.

Both translational and rotational diffusion are super-diffusive at long times for small active forces.

Abstract

We study the structural and dynamical behaviors of a diblock copolymer chain in a bath of active Brownian particles (ABPs) by extensive Brownian dynamics simulation in a two-dimensional model system. Specifically, the A block of chain is self-attractive, while the B block is self-repulsive. We find, beyond a threshold, the A block unfolds with a pattern like extracting a woolen string from a ball. The critical force decreases with the increase of the B block length,NB, for short cases, then keeps a constant with further increase of NB. In addition, we find a power law exists between the unfolding time of chain and active force, Fa, as well as NB. Finally, we focus on the translational and rotational diffusion of chain, and find that both of them remain supper-diffusive at the long time limit for small active forces due to an asymmetry distribution of ABPs. Our results open new routes for manipulating polymer's behaviors with ABPs.