This clip shows new results for polymber melts of branched bead-spring chain molecules obtained by nonequilibrium molecular dynamics (NEMD) simulations of a Couette flow. The beads of these molecules are connected by finitely extendable nonlinear springs. A multiple time scales algorithm has been extended to nonequilibrium situations for integration of the equations of motion. Our model fluids exhibit shear thinning and nonzero normal-stress differences. We have performed simulations both at constant volume and at constant pressure for melts of both linear (up to 50 beads) and branched chains. Here we show a simulation for branched chain models. We find for the branched chains that the length of the side groups largely enhances the viscosity at low shear rates. This is consistent with experimental observations. [Xu, A., J.J. de Pablo and S. Kim, "Transport properties of polymer melts from nonequilibrium molecular dynamics, J. Chem. Phys. 102 (14), 5836-5844 (April 8, 1995)].

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