Simulational Tests of the Rouse Model

Abstract

An extensive review of literature simulations of quiescent polymer melts is given, considering results that test aspects of the Rouse model in the melt. We focus on Rouse model predictions for the mean-square amplitudes (Formula presented.) and time correlation functions (Formula presented.) of the Rouse mode (Formula presented.). The simulations conclusively demonstrate that the Rouse model is invalid in polymer melts. In particular, and contrary to the Rouse model, (i) mean-square Rouse mode amplitudes (Formula presented.) do not scale as (Formula presented.), N being the number of beads in the polymer. For small p (say, (Formula presented.)) (Formula presented.) scales with p as (Formula presented.) ; for larger p, it scales as (Formula presented.). (ii) Rouse mode time correlation functions (Formula presented.) do not decay with time as exponentials; they instead decay as stretched exponentials (Formula presented.). (Formula presented.) depends on p, typically with a minimum near (Formula presented.) or (Formula presented.). (iii) Polymer bead displacements are not described by independent Gaussian random processes. (iv) For (Formula presented.), (Formula presented.) is sometimes non-zero. (v) The response of a polymer coil to a shear flow is a rotation, not the affine deformation predicted by Rouse. We also briefly consider the Kirkwood–Riseman polymer model.