Polymer Single File Diffusion: A phase diagram

We use Langevin Dynamics (LD) simulations to investigate the single file diffusion (SFD) of flexible linear polymer molecules in a dilute solution confined to a narrow tube. The transition from SFD, where the mean-square displacement scales like〈x²〉∼ t^1/2, to normal diffusion with〈x²〉∼ t, is studied as a function of the parameters that control polymer confinement and "swapping", such as the diameter of the channel, the polymer concentration, and the polymer contour length and radius-of-gyration. We propose a phase diagram describing different diffusion regimes. We also map this problem onto a modified one-dimensional Lattice Random Walk algorithm where a diffusing particle represents a polymer center of mass. In order to model the polymers entanglement and disentanglement processes, we allow several objects to temporarily share the same lattice site and diffuse together. Extensions of our work to polydisperse polymer solutions, one-dimensional electrophoresis, ring polymers, and DNA mapping are discussed.