Kinetics for Micelle-Monomer Association-Dissociation Reaction of Surfactants with Hydrophobic Counterions

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Abstract
A pressure-jump technique and a spin label technique were applied to the kinetic investigation of the association-dissociation reactions between monomer and micelle in surfactant solutions of STS, TMTS, TETS, and TPTS. The rate constants for the reactions were determined at several temperatures by the pressure-jump experiment. The ESR spectra of a spin probe, 5-SAL, solubilized in the micelles were analyzed in terms of the rotational correlation time, τc. A linear relationship was found between kd, the dissociation rate constant, and τc−1. This indicates that the dissociation rate depends on the fluidity of the micellar interior, and is in accord with the picture drawn by Aniansson et al. for the dissociation process. A qualitative discussion is presented on the activation parameters estimated from the present results according to the scheme presented by Aniansson et al.