Dynamics of entangled polymer melts: A computer simulation

Abstract

As a model for dense polymer solutions or melts we consider an ensemble of n freely jointed chains consisting of N rigid links in a box. A Lennard‐Jones interaction is taken to model repulsive and attractive interactions between the units of the chains. Dynamics is introduced into the model by allowing for stochastic rotations of the beads of the chains, where the transition probability satisfies detailed balance and only such rotations are allowed which do not lead to any intersection of chains, in order to take entanglement restrictions into account. Although the chains treated by the simulation are very short (N = 16), with increasing density and/or decreasing temperature we do find a transition from a regime of essentially Rouse‐like dynamics (with decreased mobilities) to a glass‐like state, where the ’’monomer’’ displacements are very small and follow different power laws of time than in the Rouse model. We also treat the case where all chains apart from the mobile one are strictly frozen in, so that the mobile chain moves through fixed obstacles. We clearly confirm the de Gennes reptation mechanism for this case, while it does not become effective in the other cases above where either ’’tube rearrangement’’ is not negligible or all motions are more or less frozen. The experimental relevance of these results is briefly discussed.