PHASE-BEHAVIOR AND MICROSTRUCTURE OF NONAQUEOUS MICROEMULSIONS

Phase behavior of glycerol, propylene glycol, hydrocarbon, and alkylpolyglycol ether (CiEj) surfactant microemulsions has been studied. Surfactant solubility in the polar organic phase (a mixture of glycerol and propylene glycol) decreases when glycerol content is increased, and a 2-3-2 phase transition is observed at constant temperature. The phase behavior usually observed in water microemulsions as a function of temperature is observed here as a function of the fraction of glycerol in the polar organic phase. Phase behavior is reported as a function of oil solvophobicity and the surfactant solvophilic-lipophilic balance and is compared to a well-established model developed for aqueous microemulsions. Porod analysis of small-angle X-ray scattering (SAXS) measurements indicates the presence of interfaces; thus the fluids are microstructured. The SAXS measurements suggest that aqueous and nonaqueous microemulsions are structurally similar. © 1990 American Chemical Society.