TY - JOUR
T1 - Polymer brushes under shear
T2 - Molecular dynamics simulations compared to experiments
AU - Singh, Manjesh K.
AU - Ilg, Patrick
AU - Espinosa-Marzal, Rosa M.
AU - Kröger, Martin
AU - Spencer, Nicholas D.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/4/28
Y1 - 2015/4/28
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.langmuir.5b00641
DO - 10.1021/acs.langmuir.5b00641
M3 - Article
C2 - 25830715
AN - SCOPUS:84928665988
SN - 0743-7463
VL - 31
SP - 4798
EP - 4805
JO - Langmuir
JF - Langmuir
IS - 16
ER -