Brush in the bath of active particles: anomalous stretching of chains and distribution of particles

TL;DR

This study investigates how active particles influence polymer brushes, revealing anomalous particle penetration, chain stretching behaviors, and a surprising compression effect at high self-propelling forces through simulations.

Contribution

It introduces new insights into the effects of active particles on polymer brush structure and dynamics, highlighting anomalous density distributions and chain stretching behaviors.

Findings

Increased particle penetration with higher self-propelling force.

Particle density inside the brush surpasses outside at large forces.

Chains exhibit weak compression at high grafting density and forces.

Abstract

The interaction between polymer brush and colloidal particles has been intensively studied in the last two decades. Here we consider a flat chain-grafted substrate immersed in a bath of active particles. Simulations show that an increase in the self-propelling force causes an increase in the number of particles that penetrate into the brush. Anomalously, the particle density inside the main body of the brush eventually becomes higher than that outside the brush at very large self-propelling force. The grafted chains are further stretched due to the steric repulsion from the intruded particles. Upon the increase of the self-propelling force, distinct stretching behaviors of chains were observed for low and high grafting densities. Surprisingly, we found a weak descent of the end-to-end distance of chains for high grafting density and very large force which is reminiscent of the compression effect of a chain in the active bath.