CHANGE IN SIZE AND COMPOSITION OF MIXED MICELLES WITH CONCENTRATION IN ANIONIC CATIONIC SURFACTANT SOLUTIONS

Light scattering intensities and self-diffusion coefficients of both components have been measured on the sodium dodecyl sulfate (SDS)/octyltrimethylammonium bromide (OTAB)/water system as a function of total surfactant concentration, c, at different mixing ratios (below c of 1% by weight). In the SDS-rich side, as c is decreased, i.e., as the phase boundary between the mixed micelle region and the precipitation region is approached, micelles grow and the mole fraction of OTAB in the mixed micelle, x2m, increases. It is also shown that the mixed micelles grow rapidly when x2m exceeds about 0.25. © 1990.