Thermodynamically consistent reptation model without independent alignment

Abstract

The Poissonian character of the reversible part of nonequilibrium dynamics is exploited here in order to determine a dynamically consistent expression for a reptation model without the independent alignment assumption. It is shown that the previously proposed form by Doi and Edwards for such a model is compatible with the GENERIC formalism of nonequilibrium thermodynamics [Phys. Rev. E 56, 6620 (1997); 56, 6633 (1997)] only after two changes are made: (a) the production term in the evolution equation involves an average of the orientation dyadic uu over the entire internal phase space, and (b) the extra stress tensor involves an additional term, qualitatively different from the one representing the original Doi–Edwards expression. The predictions of the new model for the stress after double shear strain with flow reversal are shown to be realistic, demonstrating irreversibility effects, in contrast to the model with the independent alignment approximation.