ULTRASONIC RELAXATION AND ELECTROCHEMICAL MEASUREMENTS ON MONOMER MICELLE EXCHANGE IN DODECYLPYRIDINIUM BROMIDE SOLUTIONS CONTAINING ADDED SODIUM-BROMIDE

The ultrasonic relaxations associated with the perturbation of the monomer/micelle equilibrium in dodecylpyridinium bromide (DPBr) have been measured in the presence of 10(-4) and 10(-1) mol dm-3 sodium bromide (NaBr). The emf of a specially constructed dodecylpyridinium cationic surfactant membrane electrode relative to, successively, a bromide ion, sodium ion, and also a liquid junction electrode has been measured, and the monomer concentration of DP+ in the micellar range and the effective degree of micellar dissociation have been evaluated. The combined dynamic and equilibrium data have been used to investigate the kinetics of the monomer/micelle exchange process by using different versions and modifications of the so-called fast relaxation time equation of Aniansson and Wall and also an alternative approach to investigate kinetics-a phenomenological treatment. The scope and limitations of these approaches to derive new micellar parameters are discussed. From the concentration dependence of the amplitude of the ultrasonic relaxation the volume change associated with the monomer/micelle equilibria has been estimated. In addition density measurements and light scattering measurements were taken.