Role of oxygenated oils in n-alkyl β-D-monoglucoside microemulsion phase behavior

The phase behavior of mixtures of water, alkyl ethylene glycol ethers (C_kOC₂OC_k) and n-alkyl β-D-glucopyranosides (C_mG₁) is systematically reported as a function of temperature and composition. Previous work has shown that C_mG₁ are nearly insoluble in alkanes, and ternary mixtures of water-alkane-C_mG₁ produce stable emulsions. Replacing alkanes with more hydrophilic alkyl ethylene glycol ethers increases the solubility of C_mG₁ in the oil. The well-known 2-3-2 phase sequence is observed in water-C_kOC₂-OC_k-C_mG₁ mixtures with increasing temperature, indicating that C_mG₁'s partition into the oil at higher temperatures. This microemulsion phase behavior closely resembles that of mixtures made with water, oil, and other nonionic surfactants, e.g., n-alkyl polyglycol ethers (C_iE_j), and both tricritical phenomena and general patterns of phase behavior are observed.