Testing the Ability of the Slip-Spring Model to Describe Constraint Release Effects Using Experimental Linear and Nonlinear Rheology

We tested the ability of the discrete slip-spring (DSS) model, which is a variation of the original model of [], to predict, using a single set of parameters, a uniquely complete set of linear viscoelastic mechanical and dielectric data for both linear and star monodisperse and probe cis-polyisoprene chains with and without constraint release [ ]. For the linear polymers, the DSS model reproduces well the mechanical and dielectric properties, while for the star polymers, the mechanical properties are reasonably captured, but the dielectric predictions show a relaxation roughly 70% longer than the experimental data when the branch point is held fixed. This deviation is almost eliminated in some cases and cut roughly in half in others by allowing the branch point to move in response to spring and Brownian forces. In the nonlinear regime, the DSS model can address the effect of the entanglement loss and reproduces well the strain rate dependence of the steady-state shear viscosity of linear chains. These results establish a baseline level of accuracy of slip-spring models, against which the predictions of tube models and other slip-link models can be compared, which should ultimately lead to model improvements.