Studies on the phase behavior and solubilization of the microemulsion formed by surfactant-like ionic liquids with ε-β-fish-like phase diagram

The phase behavior and the solubilization of the microemulsion systems surfactant-like ionic liquids 1-hexadecyl-3-methylimidazolium bromide (C(16)mimBr), 1-tetradecyl-3-methylimidazolium bromide (C(14)mimBr), or 1-dodecyl-3-methylimidazolium bromide (C(12)mimBr)/alcohol/alkane/brine have been studied with epsilon-beta-fish-like phase diagram method at 40 degrees C and an oil-to-water mass ratio of 1:1. From the epsilon-beta-fish-like phase diagram, the physicochemical parameters, such as the mass fraction of alcohol in the hydrophile-lipophile-balanced interfacial layer (A(S)), and the solubilities of ionic liquid (S-O) and alcohol (A(O)) in alkane phase, were calculated. The solubilization of the microemulsion system has been discussed based on the epsilon-beta-fish-like phase diagram. The smaller the oil molecule, the longer the alcohol chain length, and the larger the NaCl concentration in water, the larger the solubilization of the microemulsion system. In this paper, the solubilization of the microemulsion stabilized by both C(12)mimBr and sodium dodecyl sulfonate (sodium dodecyl sulfate) was also investigated with the epsilon-beta-fish-like phase diagram. The unequimolar composite of anionic and cationic surfactants can avoid the sedimentation aroused by the strong electrostatic attraction, and an obvious synergism effect in solubilization was obtained.