Complex wetting phenomena in liquid mixtures: frustrated-complete wetting and competing intermolecular forces

Abstract

We give a phenomenological overview of recently discovered complex wetting states in simple liquid mixtures relevant to both fundamental research and industrial applications such as oil recovery. Alkanes on water show a sequence of two wetting transitions, from partial wetting to `frustrated-complete wetting', and finally to complete wetting: a first-order thin-thick transition between a microscopic and a mesoscopic adsorbed alkane film is followed by a long-range critical wetting transition to a macroscopic wetting layer. The existence of the new `frustrated-complete wetting' state follows from a competition between short-range and long-range components of the intermolecular forces, the latter opposing wetting. The effective long-range forces between interfaces consist of Debye dipolar and London dispersion contributions, which can also be in mutual competition. The London component is ultimately responsible for the frustration preventing complete wetting at ambient temperatures and pressures.