Interface tension, interface Gibbs free energy and contact angle

The surface and interface tension and/or surface and interface Gibbs free energy were considered based on the Young equation. To solve this equation with regard to the solid surface tension and/or the solid Gibbs free energy the relationships between the solid-liquid interface tension or interface energy and surface tension or Gibbs surface energy of solid and liquid must be known. For this reason, there were discussed many approaches to these relationships. They were divided into two groups. One group includes the approaches assuming that the interface tension or interface energy of the solid-liquid (liquid-liquid) does not depend on the type of intermolecular interactions in the solid and the liquid but only on the value of their surface tensions. In turn, the second group of the approaches assume that the solid-liquid (liquid-liquid) interface tension or Gibbs energy depends on the type of intermolecular interactions in the solid and the liquid, and not only on the value of the surface tension of the liquid and the solid. The components and parameters of solid and liquid surface tension resulting from different type of intermolecular interactions were considered depending on the types of the approach. Taking into account these approaches their applicability for predicting interface tensions and wettability of solids by liquids with different hydrophobic and hydrophilic properties was analyzed. Thus, based on the thermodynamics of irreversible processes, it was assumed, in accordance with the Young's statements, that the contact angle value is a function of the surface tension of the liquid and solid at the time of measurement. Therefore, the literature values of surface and interface free energy determined from the Young's equation were treated as the values of surface and interface tensions.