Physicochemical Studies On Microemulsion With An Ionic Liquid

Some basic properties, microstructure and application of ionic liquid microemulsion systems have been studied by thermodynamics and kinetics methods.Phase equilibrium and critical phenomena of the microemulsions with an ionic liquid have been studied. The coexistence curves (T, n) of ionic liquid microemulsions of water-[bmim][BF4]/1,4-di(2-ethyl-l-hexyl)sulphosuccinate(AOT)/decane and [bmim][BF4]/Triton X100/cyclohexane were determined by refractive index measurements in the critical regions, where T and n are temperature and refractive index, respectively. The coexistence curves of (T, n) were converted to(T,(?)) and (T, (?)), (0 and y are volume fraction and effective volume fraction, respectively) by the standard curves. The critical exponentβ, which described the shape of the coexistence curve, the critical amplitudes B, the amplitude of Wegner correction terms B1 and the diameters of coexistence curves pd were deduced. The effects of the concentration of [bmim][BF4] (x) and dispersed droplet sizes on the critical behavior of the ionic liquid microemulsions were discussed. Our main conclusions are that:(1) The water-[bmim][BF4]/AOT/decane microemulsions have lower critical temperatures Tc and the Tc increased with x. On the contrary, the upper critical temperature was obtained for all the [bmim][BF4]/Triton X100/cyclohexane ionic liquid microemulsions, and the Tc increase with the dispersed droplet sizes. (2) Critical volume fractions of water-[bmim][BF4]/AOT/decane microemulsions were smaller than those of the water/AOT/decane system; and the critical volume fraction increased with dispersed droplet sizes for [bmim][BF4]/Triton X100/cyclohexane systems. (3) The values ofβapproach the 3D-Ising value of 0.3265 for two systems in the regions sufficiently close to the critical temperatures.Kinetics of a Diels-Alder Reaction of N-Ethylmaleimide (EM) with 2,3-Dimethyl-1,3-butadiene (DB) in the H2O/AOT/isooctane microemulsion with the ionic liquid were studied for the first time. The second-order rate constants were determined by spectrophotometry in various ionic liquid microemulsions. The effect of variety factors on the DAR rate was investigated and was interpreted. The experimental results shown that the reaction rate in the ionic liquid microemulsion is enhanced than that obtained in pure isooctane and in generic microemulsion, and the rate constant (k2) increase withωand AOT concentration. The results indicate that high temperature accelerate the reaction and the activation energy Ea decrease withωincrease.