Formation Kinetics of an Emulsion in the System Water, Didodecyldimethylammonium Bromide, and Sodium Xylenesulfonate

The ternary phase diagram, the colloidal structures involved and the kinetics of an unusual emulsion formation in the system water, sodium xylenesulfonate (a hydrotrope) and didodecyldimethylammonium bromide (a surfactant) were determined using visual observation, optical microscopy, light scattering, electrical conductance and the stop-flow method. The results showed as expected that addition of the hydrotrope to the surfactant-water lamellar liquid crystal caused a disordering of it to an isotropic liquid, a microemulsion, but, surprisingly, for lesser hydrotrope/surfactant ratios the result of the addition was more ordered structures; a cubic liquid crystal and a plastic crystal. The results of stop-flow/light scattering analysis of the microemulsion-water mixing into an emulsion showed a marked reduction in scattering after mixing with decay times in the 2–3 seconds range but also the presence of anisotropic material which is found only outside the realm of mixing. This complex behavior after formation was explained by the difference in the kinetics of formation of different association structures. CROATICA CHEMICA ACTA CCACAA 71 (4) 837¿851 (1998)