A TERMINALLY ANCHORED POLYMER-CHAIN IN SHEAR-FLOW - SELF-CONSISTENT VELOCITY AND SEGMENT DENSITY PROFILES

The behavior of a terminally anchored freely-jointed bead-rod chain, s ubjected to solvent shear flow, was investigated via Brownian dynamics simulations. Previous calculations have been improved by computing th e segment density and fluid velocity profiles self-consistently. The s egment density distributions, components of the radius of gyration, an d chain attachment shear and normal stresses were found to be sensitiv e to low values of shear rate. Additionally, it was found that the thi ckness of a model polymer layer was a strong function of the shear rat e, and that the functional dependence on shear rate changed dramatical ly as the chain length increased. For the longest chains studied, the thickness of the model polymer layer first increased as the shear rate increased, passed through a maximum, and then decreased at high shear rates, in accordance with experimental results in theta solvents. The se results suggest that a dilute or semi-dilute layer model may explai n hydrodynamic behavior previously thought to be due to the entangleme nts that occur in dense surface bound polymer layers.