title: Polymer Brushes under Shear: Molecular Dynamics Simulations Compared to Experiments.
abstract: Surfaces coated with polymer brushes in a good solvent are known to exhibit excellent tribological properties. We have performed coarse-grained equilibrium and nonequilibrium molecular dynamics (MD) simulations to investigate dextran polymer brushes in an aqueous environment in molecular detail. In a first step, we determined simulation parameters and units by matching experimental results for a single dextran chain. Analyzing this model when applied to a multichain system, density profiles of end-tethered polymer brushes obtained from equilibrium MD simulations compare very well with expectations based on self-consistent field theory. Simulation results were further validated against and correlated with available experimental results. The simulated compression curves (normal force as a function of surface separation) compare successfully with results obtained with a surface forces apparatus. Shear stress (friction) obtained via nonequilibrium MD is contrasted with nanoscale friction studies employing colloidal-probe lateral force microscopy. We find good agreement in the hydrodynamic regime and explain the observed leveling-off of the friction forces in the boundary regime by means of an effective polymer-wall attraction.
authors.forename: Manjesh K
authors.initials: MK
authors.lastname: Singh
authors.affiliation: §School of Mathematical and Physical Sciences, University of Reading, Reading RG6 6AX, United Kingdom.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ilg
authors.affiliation: ∥Laboratory for Smart Interfaces in Environmental Nanotechnology, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Espinosa-Marzal
authors.forename: Martin
authors.initials: M
authors.lastname: Kröger
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Spencer
mesh_terms: D003911:Dextrans / Q000737:chemistry*; D056004:Molecular Dynamics Simulation
chemical_list: D003911:Dextrans