Dynamic surface properties of solutions of phosphine oxides: A capillary wave study

The characteristics of capillary waves on the surface of aqueous solutions of dimethylalkyl phosphine oxides have been measured as a function of frequency and surfactant concentration. The damping coefficient for solutions of dodecyldimethyl phosphine oxide increased with concentration, passed through a local maximum below the CMC, and was independent of concentration above the CMC. For solutions of decyldimethyl phosphine oxide, a second maximum is observed at the CMC and the damping decreases considerably in the micellar region. This effect can be explained by an influence of the micellization kinetics on the dynamic surface elasticity and was not observed earlier for solutions of nonionic surfactants. The results are used to calculate the characteristic time of the slow step of the micellization process. (C) 1997 Academic Press.