When a drop of oil is placed on the water surface, three wetting states can be realized by the competition between the long-range and short-range surface forces. For liquid alkanes, the long-range contribution is dominated by the dispersion interaction of the water with the air across the oil film and the short-range contributions are implicitly connoted in the initial spreading coefficient. The partial wetting state, in which the oil molecules do not spread on water even in the molecular level but remain as lenses, occurs when both the short- and long-range forces prevent lenses from spreading. On the contrary, when both forces favor spreading, the water surface is covered by a uniform film (complete wetting state). In the pseudo-partial wetting state, a microscopically thin film is in equilibrium with lenses as a result that the short-range force favors spreading but the long-range force prevents it. In this paper, we will summarize the wetting behavior of alkanes on the water surface based on the above mentioned theory. Furthermore, we also demonstrate the relation between the surface freezing of long-chain alkanes and the freezing transition of pseudo-partial wetting film of them on the surfactant solutions.

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Dispersed systems consisting of fluids are represented by emulsions and foams. Colloidal particles act as efficient stabilizers for the dispersed systems, like conventional surfactants, by adsorbing at the fluid interfaces. The wettability of colloidal particles at fluid interfaces has been thought to be one of the most important factors to control properties of the fluid dispersed systems. Herein several ways to tune particle wettability in stabilizing fluid dispersed systems consisting of air and liquids are presented with an emphasis to describe incorporation of surface roughness effects into particle wetting of particles at fluid interfaces.

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