Rheological evidence for a dynamical crossover in polymer melts via nonequilibrium molecular dynamics

A certain "critical" molecular weight controls rheological properties of the multibead finitely extensible nonlinear elastic (FENE) chain model polymer melt, The rheological crossover manifests itself in a change of power law behavior for the viscous properties at a critical number of beads per chain N-c = 100 +/- 10. This finding confirms a newly proposed relationship between dimensionless critical weight, characteristic length, and flexibility which we obtain as a side result. Results further suggest that the entanglement molecular weight N-e for the flexible FENE chain model could he comparable in size or even larger than its critical molecular weight N-c.