Optimizing the Surface-Active Performances of Cat-Anionic Mixtures: A Short Review

Mixtures of oppositely charged surfactants are used for applications requiring extensive foaming. This holds true for cat-anionic systems. Their bulk behavior is known in detail, when surface, or interface, properties do not attract the same attention. The thermodynamic features of such systems and the strategies interrelating the behavior in bulk to that at surfaces are outlined. Such systems are strongly not ideal. So, the interaction parameters for bulk and surface phases, β_surf and β_mic, respectively, are introduced. Efforts to connect the two quantities were made. The definition of interaction parameters comes from the regular solution theory. Originally applied to micelle formation, it was later extended to the saturation of fluid surfaces. In this context, the interaction parameters were applied to the surface properties of selected cat-anionic systems and their links with bulk ones discussed.