SHEAR-RATE DEPENDENCE OF THE INTRINSIC-VISCOSITY OF BEAD-AND-SPRING CHAINS - HYDRODYNAMIC INTERACTION AND EXCLUDED-VOLUME EFFECTS

The shear-rate dependence of the intrinsic viscosity of the bead-and-spring (or Rouse) model for polymer chains with rigorous inclusion of hydrodynamic interaction (HI) and excluded volume (EV) is studied, for chains of varying length, using the Brownian dynamics simulation technique. The simulation results describe a transition from the zero-shear-rate viscosity, which depends strongly on HI and EV, to the region of very high shear rate, where the simulated viscosity is found to be that corresponding to the absence of HI and EV. As the latter is larger than the former when the chain is long enough, a shear-thickening behaviour is predicted for long bead-and-spring chains. The dumbbell model, which is the shortest chain, gives the wrong, opposite, prediction.