Relationship between Micellar Lifetime and Foamability of Sodium Dodecyl Sulfate and Sodium Dodecyl Sulfate/ 1-Hexanol Mixtures

The interface between air and surfactant solution expands rapidly during the foam generation process. Surfactant molecules in the solution should adsorb onto the newly created surface to stabilize foam. As surfactant monomers adsorb on the surface, micelles disintegrate to provide additional monomers to adsorb on the expanding interface of foam. If micelles are very stable, they cannot rapidly provide monomers to the newly created surface. Hence, the kinetics of disintegration of micelles should influence the foaming ability of surfactant solutions. This study attempts to test this hypothesis and to establish the framework of knowledge on the micellization kinetics and the foamability of surfactants. In this study the relationship between the micellar lifetime and foaming ability of aqueous surfactant solutions was elucidated by the pressure-jump technique and air-generated foam columns, respectively, at 25 OC. The results showed that the average lifetime (i.e. the stability) of micelles reached a maximum value at a specific surfactant concentration. At the same surfactant concentration, we found the minimum foamability. With this approach, a correlation between micellar relaxation time and foamability of the surfactant solutions was established.