RHEOLOGY OF WET POLYMER BRUSHES VIA BROWNIAN DYNAMICS SIMULATION - STEADY VS OSCILLATORY SHEAR

The rheology of solvent-filled polymer brushes under steady and oscill atory shear is studied by Brownian dynamics simulation. The flow field is solved self-consistently with the polymer dynamics. We find that u nder steady flow the brushes are shear thinning in both normal forces and shear viscosity. During oscillatory flow, extreme shear thickening occurs when the ratio of the Weissenberg number to the dimensonless f low frequency Wi/omega approximate to 3. Shear-induced diffusion is sh own to create this thickening. These findings serve to explain the rec ent measurements made by Klein et al.