Chain Model for Concentrated Solutions and Melts

Abstract

A dense collection of repulsive FENE chains serves as a suitable microscopic model for both entangled and unentangled polymer melts. We will consider once more linear and monodisperse chains although FENE models are immediately applicable to polydisperse polymers with aribtrary architectures. Besides its success for the study of polymer melts at equilibrium [13,139–141], the nonlinear viscoelastic and structural properties of FENE chain models such as viscosities and scattering patterns are in accordance with experimental results for shear– and elongational flows [17, 18, 142–146]. Due to the computational demands caused by the strong increase of relaxation time with molecular weight (M) only recently it has been observed, that the basic model also exhibits the experimentally observed rheological crossover, certainly related to the ability of polymers to form knots (topological constraints) between macromolecules which is further discussed in [5, 147–154]. The crossover manifests itself in a change of power law for the zero shear viscosity at a certain M.