Measurement of the hydrophobic interaction between two hydrophobic surfaces in aqueous electrolyte solutions

The attractive force-law between two hydrophobic (hydrocarbon) surfaces in aqueous solutions has been derived from total force measurements on monolayer coated mica surfaces. This “hydrophobic interaction” is much stronger than the expected van der Waals interaction at distances below 8 nm and decays exponentially with distance. The results highlight the long-range nature of hydrophobic (solvation) forces and indicate that these forces may determine the magnitude of the energy barriers between interacting charged particles and hence the stability of hydrophobic colloids. The results are also consistent with previous experimental and theoretical estimates of the hydrophobic interaction between contacting nonpolar solute molecules in water.