On the Concept of Driving Force Applied to Micelle and Vesicle Self-Assembly

Abstract

Micellar kinetics are considered from the viewpoint of the various surfactant exchange processes which can take place and the overall driving force for dissolution/formation of micelles. The ideas are then extended to include vesicle self-assembly processes. The kinetics of these systems are usually easier to study experimentally, since the rate processes are slower, which means that structural characterization of intermediates might then be possible. Specifically, kinetic data are reported for the formation and breakdown of vesicles involving the following synthetic surfactants: sodium 6- or 7-tridecylbenzenesulfonate (SLABS), for which the system is perturbed by changing the ionic strength in order to form or break vesicles, and hexadecyldecyldimethylammonium bromide (C16C10DMABr), where vesicles are broken down to mixed micelles on addition of a single-chain alkyltrimethylammonium bromide cationic surfactant. We demonstrate that the rate of the vesicle formation/breakdown transformation is dependent on how far the final concentrations are away from the phase transition concentration conditions for formation/breakdown of the vesicles.