Studies on the phase behavior of the microemulsions formed by sodium dodecyl sulfonate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate with a novel fishlike phase diagram

The middle-phase behavior for the quaternary system of sodium dodecyl sulfonate (AS) (sodium dodecyl sulfate, SDS; sodium dodecyl benzene sulfonate, SDBS)/alcohol/oil/water has been studied with a novel ɛ–β fishlike phase diagram at 40 °C. The composition of the hydrophile–lipophile balanced interfacial layer was determined. The coordinates of the start point B and the end point E of the middle-phase microemulsion, and the solubilities of sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and alcohol in the oil phase were calculated. The solubilization power of the middle-phase microemulsion was investigated. The effects of different alcohols, oils and inorganic salts on both the phase behavior and the composition of the interfacial layer were also investigated. The shorter the carbon chain lengths of the oils and the longer the carbon chain lengths of the alcohols, the higher the solubilization of the microemulsions. The inorganic salt (NaCl) facilitates the microemulsion inversion Winsor I → III → II.