ULTRASONIC RELAXATION AND ELECTROCHEMICAL MEASUREMENTS OF THE MICELLIZATION OF SODIUM DODECYL-SULFATE AND SODIUM DIHEXYLSULFOSUCCINATE

The ultrasonic relaxation associated with the perturbation of the mono mer/micelle exchange process in sodium dodecyl sulfate and sodium dihe xylsulfosuccinate in the presence of 10(-4) (mol dm(-3)) NaBr has been studied. Membrane electrodes selective to both surfactants were const ructed and their emf measured relative to both a commercial bromide an d a sodium electrode. From these emf data the monomer concentrations o f both surfactants in the micellar range and also the degree of micell ar dissociation were measured. The kinetic parameters associated with the monomer micelle exchange process and the polydispersity of the mic elles have been evaluated using different versions of the relaxation e quation originally derived by Aniansson and Wall and also using a phen omenological treatment. Finally, the volume change during micellizatio n and the polydispersity of the micelles were evaluated from the conce ntration dependence of the relaxation amplitude. (C) 1995 Academic Pre ss, Inc.