Imperfect single-file diffusion of polymer chains: A phase diagram.

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 〈x^{2}〉∼t^{1/2}, to normal diffusion with 〈x^{2}〉∼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's center of mass. Possible extensions of this work to polydisperse polymer solutions, one-dimensional electrophoresis, and DNA mapping are discussed.