title: Do liquid films rupture due to the so-called hydrophobic force or migration of dissolved gases?
abstract: Liquid films between hydrophobic (water-repellent) interfaces are not stable. The film rupture has been attributed to the so-called hydrophobic attraction. In this paper microinterferometry experiments show that gases inherently dissolved in water have a significant effect on the film rupture. Specifically, films of ultrapure deionized water in contact with degassed oil (squalene) were stable for as long as 35 min, while the water films in contact with nondegassed oil had a lifetime of seconds. These films ruptured at film thicknesses of approximately 150 nm. The degassed oil was also purposely left in contact with air. The oil-in-water emulsion films formed between degassed oil left in contact with air for a long period of time did not last longer than a few seconds and ruptured at significantly high thicknesses (about 800 nm). The degassing effect did not change the interfacial potential (about -65 mV) and the electrical double-layer repulsion between the squalene-water interfaces. Migration of dissolved gases between oil and water caused the rupture phenomena observed.
authors.affiliation: Division of Chemical Engineering, School of Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Stoyan I
authors.initials: SI
authors.lastname: Karakashev
authors.forename: Anh V
authors.initials: AV
authors.lastname: Nguyen