Kinetics of Induced Vesicle Breakdown for Cationic and Catanionic Systems

Cationic and catanionic surfactant vesicle systems have been perturbed by addition of a single-chain surfactant to take the system from a vesicle-stable region to a micelle-stable region. The first vesicle system is based on a double-chain cationic surfactant cetyldecyldimethylammonium bromide (C16C10DMABr) and the second vesicle system is based on a mixture of anionic and cationic single-chain surfactants, namely, sodium octyl sulfate (SOS) and cetyltrimethylammonium bromide (CTAB). In both systems, vesicle breakdown will involve the initial incorporation of the single-chain surfactant into the vesicle, followed by subsequent disintegration of the vesicle. The progress of reaction has been observed by monitoring turbidity changes using a stopped-flow or conventional spectrophotometer. The rate of breakdown of vesicles was found to be linearly dependent on the concentration of added single-chain surfactant, which provides the driving force for the breakdown reaction. The breakdown reaction rates could be changed by factors up to 100 by adjusting the concentration of the solutions.