Interactions between densely grafted molten polymer brushes: scaling theories versus molecular simulations

Using molecular dynamics simulations and scaling arguments, we analyzed the interactions between two identical molten polymer brushes intermediately and strongly compressed towards each other at melt conditions. The width of the overlap region, in which monomers of the linear chains composing the two brushes interact, increases as the polymer-grafted surfaces are brought closer. If two-brush coated surfaces are as close as the characteristics size of the grafted chains, the overlap region is directly controlled by intersurface distance. At intermediate compression, the width of the overlap region scales with the end-to-end size of chain sections within the overlap region. This result is consistent with the scaling regimes in the literature. As the intersurface distance is decreased, the number fraction of chains (chains with their free ends in the overlap region) decreases with a power law. Our results could be useful for studies on tribological behavior of polymer-grafted surfaces as well as for the self-assembly of polymer coated colloids.