Jamming Crossovers in a Confined Driven Polymer in Solution

TL;DR

This study uses advanced simulations to explore how a confined polymer responds to being compressed by a moving colloid, revealing a velocity-dependent transition to high-density states and complex folding behaviors.

Contribution

It introduces a detailed simulation analysis of polymer jamming and crossover phenomena under confinement and driven conditions, highlighting velocity thresholds and state coexistence.

Findings

Polymer exhibits a velocity threshold $v^*$ for density transition.

Back end of polymer reaches high density with low MSD beyond $v^*$.

Front end remains in a high MSD, indicating coexistence of states.

Abstract

We use lattice-Boltzmann molecular dynamics (LBMD) simulations to study the compression of a confined polymer immersed in a fluid and pushed by a large spherical colloid with a diameter comparable to the channel width. We examined the chain's deformation with both purely repulsive and weakly attractive Lennard-Jones (LJ) potentials applied between the monomers. The sphere's velocity was varied over 3 orders of magnitude. The chain is in a non-dense state at low pushing velocities for both repulsive and attractive monomer interactions. When the velocity of the spherical colloid exceeds a threshold $v^*$, the back end of the chain transitions to a high density state with low mean square monomer displacement (MSD) values. The front end, however, remains in a non-dense state with high MSD indicating a pseudo two-state coexistence. This crossover is also revealed through volume per monomer and MSD as a function of the sphere's velocity. We also studied polymer dynamics by investigating folding events at different times.