Polymer (imperfect) single-file diffusion: A phase diagram

TL;DR

This study uses Langevin dynamics simulations to explore how flexible polymers diffuse in narrow tubes, identifying conditions for transition from single-file to normal diffusion and proposing a phase diagram for these regimes.

Contribution

It introduces a phase diagram for polymer diffusion regimes in narrow tubes and highlights two pathways to normal diffusion, extending understanding of polymer dynamics in confined environments.

Findings

Identified transition conditions between single-file and normal diffusion.

Mapped the problem onto a one-dimensional lattice model.

Proposed a phase diagram for diffusion regimes.

Abstract

We use Langevin dynamics (LD) simulations to investigate single-file diffusion (SFD) in a dilute solution of flexible linear polymers inside a narrow tube with periodic boundary conditions (a torus). The transition from SFD, where the time (t) dependence of the mean-square displacement scales like $\langle x^2\rangle \sim t^{1/2}$, to normal diffusion with $\langle x^2 \rangle \sim t$, is studied as a function of the system parameters, such as the size and concentration of the polymer chains and the width of the tube. We propose a phase diagram describing different diffusion regimes. In particular, we highlight the fact that there are two different pathways to normal long-time diffusion. We also map this problem onto a one-dimensional Lattice Monte Carlo model where the diffusing object represents the polymer center of mass. Possible extensions of this work to polydisperse polymer solutions, one-dimensional electrophoresis and DNA mapping are discussed.