Cavitation and the Interaction Between Macroscopic Hydrophobic Surfaces

TLDR

The study examined hydrophobic surface interactions in water using Langmuir‑Blodgett–prepared hydrocarbon and fluorocarbon monolayers. The hydrophobic attraction between macroscopic surfaces extends to 70–90 nm, driven by metastable water films, with spontaneous cavitation occurring upon contact of fluorocarbon surfaces but only after separation for hydrocarbon surfaces, suggesting that macroscopic hydrophobic interactions differ from molecular hydrophobic effects.

Abstract

The interaction in water of neutral hydrocarbon and fluorocarbon surfaces, prepared by Langmuir-Blodgett deposition of surfactant monolayers, has been investigated. The attraction between these hydrophobic surfaces can be measured at separations of 70 to 90 nanometers and thus is of considerably greater range than previously found. Spontaneous cavitation occurred as soon as the fluorocarbon surfaces were brought into contact but occurred between the hydrocarbon surfaces only after separation from contact. The very long range forces measured are a consequence of the metastability of water films between macroscopic hydrophobic surfaces. Thus the hydrophobic interaction between macroscopic surfaces may not be related to water structure in the same way that the hydrophobic effect between nonpolar molecules is related to water structure.