Tracer diffusion of zwitterionic and ionic mixed micelles. Effect of micellar size and charge

Diffusion coefficients of pyrene solubilized in mixed micelles of 3-(N-tetradecyl-N,N-dimethylammonio)propanesulfonate (C(14)DAPS) and sodium octadecanesulfonate (C18SO3Na) or sodium decanesulfonate (C10SO3Na) have been measured in aqueous NaBr solutions at 298.2 K. The diffusion coefficients decrease with increasing molar ratio of C18SO3Na or C10SO3Na to C(14)DAPS. The diffusion coefficients for the mixed micelles are lower in water than in salt solutions. The results are interpreted in terms of the size and charge of the mixed micelles.