Thermodynamic theory of thin liquid films including line tension effects

This paper presents the contemporary state-of-art of the phenomenological thermodynamic theory of the thin foam and emulsion films, both symmetrical and asymmetrical ones. The roots of this theory are in the Gibbs' theory of capillarity. Two basic approaches — with two Gibbs dividing surfaces and with three surfaces of tension, are described. The generalization of the theory for systems with more complex geometry is commented. The ways of determining of the thermodynamic thickness of the film are described. The basic thermodynamic quantities of the thin film: disjoining pressure, tension of the film and surface tension of the film, are defined. The tangential mechanical equilibrium conditions with two types of contact angles, θ_h, and θ₀, are discussed. The effect of line tension of the three-phase contact-line perimeter on the film contact angles is elucidated.