The microemulsion phase in the didecyldimethylammonium bromide/dodecane/water system.: Phase diagram, microstructure, and nucleation kinetics of excess oil phase

We report on a study dealing with the properties of the microemulsion phase formed by the synthetic double-chained surfactant didecyldimethylammonium bromide in the presence of water and dodecane. It is shown that the microemulsion phase in this system connects to the water corner. The upper boundary of the microemulsion at high water contents is concave downward, and an explanation is provided for this effect. The microstructure of the microemulsion is probed using component resolved NMR diffusion methods. The results indicate that upon decreasing water content, the microemulsion becomes bicontinuous and at a rather well-defined concentration there is a discontinuity in the water diffusion implying that at this point the microemulsion becomes truly bicontinuous. Finally, on account of the appearance of the extension of the microemulsion region at high water content, it is possible to study the nucleation kinetics of the excess oil phase as the system is perturbed by the addition of water such that one enters the two-phase region microemulsion/excess hydrocarbon.