Middle-phase microemulsions of green surfactant alkyl polyglucosides

The microemulsion behavior in the quaternary system alkyl polyglucoside (C₈G_1.46, C₁₀G_1.54)/1-butanol/cyclohexane/water has been studied at 40°C with the alcohol concentration scanning and the fishlike phase diagram methods. Increasing δ at a constant γ causes a phase inversion from an oil-in-water microemulsion in contact with excess oil (Winsor 1 or 2l- ) to a water-in-oil microemulsion in contact with excess water (Winsor II or -2) via a middle-phase microemulsion in contact with excess oil and water (Winsor III or 3). By using the simple mass balance equation and the HLB plane equation, the mass fraction of 1-butanol in the interfacial layer, S ₂ ^s , the monomeric solubilities of APG and 1-butanol, S₁ and S₂, in the oil phase, and the mass fractions of APG and 1-butanol in the interfacial layer (C₁ and C₂) have been calculated, respectively. The effects of different alcohols, aqueous media and oils on the phase behavior and the composition of the interfacial layer are also investigated. It is found that the alcohols with longer hydrocarbon chain, oil molecules with smaller molecular volume and the addition of inorganic salt can increase the solubilization of the microemulsions.