Phase behavior and characterization of ionic liquids based microemulsions

A microemulsion based on imidazolium ionic liquids (ILs), 1-octyl-3-methylimidazolium chloride [omim][Cl], as a surfactant, a hydrophobic IL as a substitute for traditional organic solvent, 1-butyl-3-methylimidazolium hexaflourophosphate [bmim][PF6] and water was formed at 25 °C. The phase behavior of this ternary system was investigated. The formation of [bmim][PF6]-in-water regions was identified by electrochemical methods using potassium hexacyanoferrate K4Fe(CN)6 and ferrocene as electroactive probes and dynamic light scattering (DLS). A highly stable nano-sized microemulsion with an average size of 3 nm and narrow size distribution was obtained. The investigation of the phase behavior of the system at equal amounts of [bmim][PF6] and water at different temperatures indicates that when the weight fraction of [omim][Cl] is 0.6, a single phase, temperature insensitive microemulsion was formed. Solubilization of lipophilic dye, 4-(p-nitrophenyl azo)-pyrocatechol(NAP) and also vitamin K3 in this media show that this IL-based microemulsion has potential applications in biological extractions or as solvents for enzymatic reactions.