Shear deformation of low-density polymer brushes in a good solvent

TL;DR

This paper models the behavior of a single polymer chain tethered to a substrate under shear flow and good solvent conditions, revealing that shear causes chain stretching but does not alter the perpendicular density profile.

Contribution

It introduces a new theoretical framework for hydrodynamic interactions in polymer brushes under shear flow within a self-consistent field approach.

Findings

Chain stretches along shear flow direction.

Perpendicular density profile remains unchanged under shear.

Results agree with neutron scattering experiments.

Abstract

Self-consistent field approach is used to model a single end-tethered polymer chain on a substrate subject to various forces in three dimensions. Starting from a continuous Gaussian chain model, the following perturbations are considered: (i) hydrodynamic interaction with an externally imposed shear flow for which a new theoretical framework is formulated; (ii) excluded volume effect in a good solvent, treated in a mean field approximation; (iii) monomer-substrate repulsion. While the chain stretches along the flow, the change of the density profile perpendicular to the substrate is negligible for any reasonable simulation parameters. This null effect is in agreement with multiple neutron scattering studies.