Compression of high grafting density opposing polymer brushes using molecular dynamics simulations in explicit solvent.

Opposing polymer brush layers at high grafting density were examined under confinement and characterized with respect to structure and interaction forces using molecular dynamics simulations in an explicit solvent. The brush system underwent a static compression, where the system is simulated at several discrete separation distances. These simulations are all at the same solvent chemical potential as a non-interacting reference state to produce a realistic compression. Normal pressure-distance profiles were generated and compared to density profiles at each separation distance to determine structure-property relationships. Significant interpenetration of brush layers occurred at high compression, to the extent that each brush reached the opposing surface. Higher interpenetration corresponded to a sharp increase in the pressure-distance curve, suggesting a correlation between interpenetration and interaction forces. We find clear differences from literature values using implicit solvent techniques.