Statistics of polymer adsorption under shear flow

Abstract

Using nonequilibrium Brownian dynamics computer simulations, we have investigated the steady state statistics of a polymer chain under three different shear environments: (i) linear shear flow in the bulk (no interfaces), (ii) shear vorticity normal to the adsorbing interface, and (iii) shear gradient normal to the adsorbing interface. The statistical distribution of the chain end-to-end distance and its orientational angles are calculated within our computer simulations. Over a wide range of shear rates, this distribution can be mapped onto a simple theoretical finite-extensible-nonlinear-elastic dumbbell model with fitted anisotropic effective spring constants. The tails of the angular distribution functions are consistent with scaling predictions borrowed from the bulk dumbbell model. Finally, the frequency of the characteristic periodic tumbling motion has been investigated by simulation as well and was found to be sublinear with the shear rate for the three setups, which extends earlier results done in experiments and simulations for free and tethered polymer molecules without adsorption.