Thermodynamic Properties of Water-Ethanol Films Formed between Hydrophobic Surfaces. Part I.

摘要

Based on thermodynamic reasoning we claim that long-ranged, solvophobic surface forces may arise in thin films of associated liquids due to formation of linear aggregates composed of spheroidal, nanosized molecular clusters. Supposedly, these aggregates can span a narrow gap between two hydrofobic solid surfaces submerged in the film-forming liquid phase, thus giving rise to attraction. Such aggregates are apparantly generated in thin water and water-ethanol films, especially below room temperature and for high mole fractions of water or ethanol, respectively. The surface force recorded for a pure water with film thickness larger than about 20 nm are found to be proportional to the number of bridging cluster aggregates per unit area that cross the mid-plane of a thin film. Moreover, the long-range-ness (decay length) was seen to depend inversely on the work of formation of the elongated middle part of a bridging cluster aggregate. Furthermore, addition of small amounts of ethanol rapidly reduce the surface force generated for pure water films with thickness of a few hundred nm.