The effects of alkyl chain lengths of sodium alkyl sulfates and n-alkanes on microemulsion formation

Abstract

The effects of alkyl chain lengths of sodium alkyl sulfates (SCN) and n-alkanes (ACN) on microemulsion formation have been investigated. The multiphase microemulsion systems studied were composed of sodium alkyl sulfates, n-alkanes having different alkyl chains, n-hexanol, and brine. These systems show a Winsor-type phase transition (Winsor I ↔ Winsor III ↔ Winsor II type) with changing salinity. At the optimum salinity for middle-phase microemulsion formation, more than 97% of the surfactant exists in the middle-phase microemulsion, and the surfactant content in it increases with increasing SCN and decreasing ACN. We found that the effects of SCN and/or ACN on microcmulsion formation will depend on the strengths of both hydrophilic and hydrophobic interactions at the oil/water interface.