Micellization model for multivalent ionic surfactants

Abstract

The micellization of surfactants comprising a multivalent ionic head and a dodecyl tail was modeled using Tanford's approach, which involves the description of the Coulombic repulsive forces via the Debye-Hückel approximation and the estimation of the hydrophobic attractive forces through the use of an empirical equation. The model predicts that a low surfactant charge (valence), a high salt concentration, and a high degree of neutralization of the surfactant charge by counterions favor micellization. It was also found that an increase in the surfactant charge leads to a decrease in the micellar aggregation number and to an increase in the critical micelle concentration (cmc). More specifically, it was determined that the aggregation numbers scale as the inverse first power of the surfactant charge, while the logarithm of the cmc's scales linearly with the surfactant charge. The predictions of our model compare favorably with theoretical and experimental findings on the micellization of amphiphilic charged block copolymers. © 1995 American Chemical Society.