(709b) Linear and Non-Linear Rheology of Melts: Simulations of Coarse Grain Polymeric Systems

The length and time scales involved in polymeric materials can span several orders of magnitude which are too computationally demanding to be address using fully atomistic models, while, the use of coarse-grained models has emerged as a useful tool to describe the  physics at the scales required, the drawback to this approach is that, soft effective interaction potentials are tipically used, meaning that interesting effects such as entangled dynamics in long polymer melts are not captured by these models. A particle-based, theoretically informed coarse-grained model for multicomponent polymeric systems is proposed to explore the dynamics of entangled polymeric melts. Entanglements are treated at the two-molecule level, through slip-springs that couple the dynamics of neighboring pairs of chains. Their inclusion in the model changes its behavior from Rouse to entangled, with scaling laws for the mean square displacement and shear viscosity consistent with those observed in tube theories and in experiments. Comparisons between simulation and experimental results are shown to be in quantitative agreement both in linear and non-linear rheology of homopolymeric melts. We use our simulation approach to explore the linear and non-linear rheological behavior of nanostructured polymeric materials.