Biased diffusion induces coil deformation via a ‘cracking-the-whip’ effect of acceleration generated by dynamic heterogeneity along a polymer chain

Abstract

We performed Brownian dynamics simulations of a single polymer with monomer diffusion biased in a field of constant activation forces. We compared coil shapes among the synchronous and non-synchronous (random and sequential) updating schemes of monomer positions. The synchronous scheme makes an ideal linear integration of monomer motions, while the random scheme mimics the real nonlinear situation holding dynamic heterogeneity along the polymer chain, and the sequential scheme represents its extremely inhomogeneous situation. We found that, in contrast to the synchronous scheme that raises no deformation, the sequential scheme accumulates the local acceleration generated by dynamic heterogeneity and reveals a ‘cracking-the-whip’ effect along the chain from one end to the other to stretch the polymer coil. Meanwhile, the random scheme accumulates the local acceleration towards the middle segment of the chain and thus raises an internal tension for coil deformation as well. Our results demonstrate the dynamic heterogeneity source of coil deformation on biased polymer diffusion, which implies a molecular-level nonlinear factor in the non-Newtonian-fluid behaviors of polymer flows. © 2014 Society of Chemical Industry