Brownian dynamics simulation of bead-rod chains under shear with hydrodynamic interaction

摘要

We have performed Brownian dynamics simulations of bead-rod chains under shear using the algorithm introduced by Ottinger. We have investigated the effect of excluded volume and hydrodynamic interactions on material functions ad configurational quantities. The model exhibits shear thinning and a negative second normal stress coefficient. We find that excluded volume interactions increase the magnitude of rheological quantities. Hydrodynamic interactions lower the viscosity for small shear rates and long chains and do not contribute significantly to the viscosity for high shear rates. The shear thinning behavior of a chain in theta solvent with hydrodynamic interactions ends at lower shear rates in comparison with other combinations of interactions. We find that chains in theta solvent expand more relative to their quiescent state than chains in good solvent for small and intermediate shear rates. Their expansion, however, is much smaller than predicted by the Rouse or Zimm model, in agreement with recent experiments. The size of chains in theta solvent with hydrodynamic interactions shrinks for very high shear rates. Chains in good solvent orient more into the shear flow than chains in theta solvent if plotted versus the absolute shear rate.