ABSTRACT
The B. V. Derjaguin’s pressure isotherm includes electrostatic, intermolecular and structural components. Contact angle hysteresis on smooth homogeneous substrates appears in the case of partial wetting, when the Derjaguin’s isotherm has a special S-shape. A theory of contact angle hysteresis on smooth homogeneous solid substrates is developed in terms of the shape of the Derjaguin’s pressure isotherm and quasi-equilibrium phenomena. The Derjaguin’s pressure isotherms with two minima are possible if they include the structural interaction consisting of two parts acting at different distances: The long-range interaction is always attractive; the short-range one can be attractive or repulsive. The expressions for the advancing and receding contact angles were obtained theoretically from the analysis of the shape of the Derjaguin’s pressure isotherm. A simplified S-shaped Derjaguin’s pressure isotherm is adopted, which allows direct calculations of static advancing/receding contact angles on deformable substrates.
