Statistics of polymer adsorption under shear flow

TL;DR

This study uses non-equilibrium Brownian dynamics simulations to analyze how polymers behave under shear flow near surfaces, revealing universal distribution patterns and tumbling dynamics across different shear environments.

Contribution

It introduces a comprehensive simulation analysis of polymer statistics under shear flow near adsorbing surfaces, extending understanding of tumbling motion and distribution functions.

Findings

Distribution functions fit a nonlinear elastic dumbbell model.

Angular distributions follow bulk scaling predictions.

Tumbling frequency scales sublinearly with shear rate.

Abstract

Using non-equilibrium 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 walls), ii) shear vorticity normal to the adsorbing wall, iii) shear gradient normal to the adsorbing wall. The statistical distribution of the chain end-to-end distance and its orientational angles are calculated within our monomer-resolved 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 set-ups, which extends earlier results done in experiments and simulations for free and tethered polymer molecules without adsorption.