Molecular dynamics simulation of spherical PEO brush: Curvature and Grafting Density Effect*

Nanoparticle modification by polyethylene oxide (PEO) is commonly used to ensure nanoparticle solubility, dispersion and protection from undesirable interactions. Using atomistic molecular dynamics simulations, we studied spherical PEO brushes grafted to gold nanoparticles of different radii and with varying grafting densities. We analyzed the scaling behavior of the radial polymer volume fraction, which is found to follow the Daoud-Cotton model, except for low grafting density when PEO adsorption onto gold surface is observed. We also investigated PEO hydration in the spherical brush and determined the existence in the surface vicinity of a dehydrated or low hydration zone, which substantially expands with an increase of grafting density and/or decrease of nanoparticle radius of curvature. The implications for water exchange within the polymer brush and with the surrounding solution will be discussed.