The role of molecular scale hydrodynamics in the kinetics of hydrophobic assembly
In order to elucidate the influence of solvent-mediated effects on the kinetics of hydrophobic assembly, we study the association of two nanoscale bodies in water. From molecular dynamics simulations with explicit solvent, we determine the free energy surfaces and hydrodynamic interactions when the particles are strongly and weakly hydrophobic. Molecular scale effects such as drying and solvent layering are found to dominate at small separations, thus giving rise to deviations from the predictions of continuum hydrodynamic theory. Regions of high friction are engendered by large and slow solvent fluctuations. In light of these findings, we also evaluate the assumption of fast solvent relaxation times that is inherent in the Brownian description of diffusion-controlled reactions. To this end a "non-Markovian Brownian theory" is introduced which accounts for slow solvent motions utilizing a coarse-grained dynamical scheme.