Thickness and Disjoining Pressure Measurements of Foam Films Stabilized by Surfactant Adsorbed Films

Abstract

In this review, (1) the effect of the surface freezing transition of cationic surfactant – alkane mixed adsorbed film on the disjoining pressure of the foam film, and (2) the relation between the foam film stability and composition of ionic-nonionic surfactant mixed adsorbed films will be discussed. In the topic (1), it is shown that the compression of the electrical double layer of the surfactant adsorbed film occurs at the surface freezing transition, leading to an abrupt foam film thickness transition. For the topic (2), the foam stability is compared for several ionic-nonionic surfactant systems varying their composition at the surface. In general, the foam film ruptures in a short time when the adsorbed film contains 70-80% of nonionic surfactant due to the weakening of the double layer repulsion in the foam film. However, if there is a strong attraction between ionic and nonionic surfactants, the adsorbed film composition becomes almost constant independent on the bulk mixing ratio of surfactants. Using this feature, a useful strategy to design a stable foam film system will be introduced. The review ends up with the future experimental plan, including the thermodynamic analysis of the film composition above the critical micelle concentration and its application to the foam film stability under continuous dilution.

graphical abstract