A Theory for the Surface Tensions and Contact Angles of Hydrogen-Bonding Liquids

The surface tensions of non-hydrogen-bonding, organic liquids can be accurately calculated from their electromagnetic properties, using an approximate form of the Lifshitz theory. A simple extension of this approach to the calculation of the surface tensions of hydrogen-bonding liquids is proposed. It is shown that the higher surface tensions of hydrogen-bonding liquids can be accounted for, with reasonable accuracy, by the increase in dispersion due to the shortened distance of approach between hydrogen-bonded atoms. Similar considerations allow calculations of contact angles on several low-energy solid surfaces in terms of molecular and electromagnetic properties. In accordance with well-known experimental observations, the calculated contact angles of both hydrogen-bonding and non-hydrogen-bonding liquids on the same low-energy surface nearly follow a single, smooth pattern.