(625a) Combining Atomistic and Mesoscopic Simulations to Understand High Shear Dynamics of Chain Molecules

Little is known concerning the dynamics of individual chain molecules at high shear rates, where most rheological models of polymeric liquids provide poor descriptions of real material behavior. Recent experimental and simulation studies have demonstrated that rheological models break down under high shear because they fail to describe the effects of the small timescale dynamics of individual polymer chains within the bulk material. This presentation showcases recent simulation efforts aimed at the development of rheological models that capture the effects of individual chain dynamics by combining detailed atomistic models with coarse-grained mesoscopic chain models of the same liquids. The detailed atomistic simulations, performed using nonequilibrium molecular dynamics, provide detailed dynamic information concerning the motions of individual chain molecules. On a longer timescale, Brownian dynamics simulations of mesoscopic bead-spring chains provide a mean-field picture of the motion of individual chains, which can be matched to the atomistic data using standard coarse-graining procedures. In this way, new models can be developed that faithfully describe the impact of the dynamics of individual molecular motions on bulk rheological response.