The aggregation of methane in aqueous solution

Molecular dynamics simulations, 1.0 ns long, of methane particles in water show the existence of a tendency for aggregation of these solutes which increases with temperature in the range 319–351 K. This is measured by a rise in the contact-configuration peak in the methane–methane radial distribution function at the expense of a decrease in the solvent-separated configuration peak. The observed solute–solute interaction reaches a maximum at 351 K before decreasing in magnitude at 358 K. These observations are consistent with an entropy-driven hydrophobic attraction.