Thinning and thickening transitions of foam film induced by 2D liquid–solid phase transitions in surfactant–alkane mixed adsorbed films.

Mixed adsorbed film of cationic surfactant and linear alkane at the air-water interface shows two-dimensional phase transition from surface liquid to surface frozen states upon cooling. This surface phase transition is accompanying with the compression of electrical double layer due to the enhancement of counterion adsorption onto the adsorbed surfactant cation and therefore induces the thinning of the foam film at fixed disjoining pressures. However, by increasing the disjoining pressure, surfactant ions desorb from the surface to reduce the electric repulsion between the adsorbed films on the both sides of the foam film. As a result, the foam film stabilized by the surfactant-alkane mixed adsorbed films showed unique thickening transition on the disjoining pressure isotherm due to the back reaction to the surface liquid films. In this review, we will summarize all these features based on the previously published papers and newly obtained results. Unlabelled Image • Mixed adsorbed film of surfactant and alkane shows freezing transition upon cooling. • Surface freezing transition induces thinning transition of foam film. • Unique foam film thickening is observed with increasing disjoining pressure. • Mechanical strength of surface frozen film stabilizes the oil-in-water emulsions. [ABSTRACT FROM AUTHOR]