摘要：

IntroductionIonic liquids (ILs) are receiving much attention as a class of solvents, because of their special physical and chemical properties, such as low volatility, non-flammability and high thermal stability.1–5They are also regarded as environmentally benign solvents for chemical reactions, separations, electrochemical applications and, more recently, for syntheses of biopolymers, molecular self-assembly and interfacial syntheses.1,6,7As potential substitutes for traditional organic solvents, they afford significant environmental benefits and can contribute to green chemistry techniques.The structure of microemulsions is a field of much current interest.8–11In order to study ionic liquid microemulsions, it is necessary to investigate the microemulsion structure and structural transitions. Although conductivity is frequently used to investigate structure and structural changes in microemulsions on the basis of percolation theory, the microstructure of the ionic liquid microemulsions cannot be differentiated through traditional conductivity measurements because ionic liquids are essentially molten salts. Several measurements of the diffusion coefficients of micelles or microemulsions have been performed using Fourier transform pulsed-gradient spin-echo NMR12–15and dynamic light scattering,16–18which provide sensitive tests of structural models of micelles or microemulsions. Also, electrochemical cyclic voltammetry has been successfully used to obtain information about the microstructure of micelles or microemulsions.10,19–35Changes in the microstructure were identified by using electrochemical probes such as ferrocene or its derivatives, ferricyanide, or methyl viologen. This detection was actually accomplished by determining diffusion coefficients of the probes which made it possible to investigate different microenvironments, in that the electrochemical reversibility of the probes was affected by the structure of the microemulsions and appeared to reflect the ease of mobility across interphases.10Chokshi and Shah28,29concluded that the diffusion coefficients probed by electrochemical probes and cyclic voltammetric measurements could also be considered self-diffusion coefficients in microemulsion systems.As is well known, solubilization of a solute and chemical reactivity are dependent on the micropolarity of dispersed droplets in reverse microemulsions. The local environment within a microemulsion droplet may be characterized by UV-Vis measurements with solvatochromic probes. The solvatochromic probes selected should be anchored to the polar core of the aggregates, to satisfy the procedural requirement of being soluble in the local environment media. Furthermore, this probe must be sensitive to the polarity of its environment and reflect the polarity through a shift of absorption maximum. Methyl orange has been successfully used to detect the microenvironment in ammonium carboxylate perfluoro polyether (PFPE) surfactant reverse microemulsions in CO2,36and TX-100 reverse micelles in cyclohexane.37Recently, our group showed that a water domain exists in Dynol-604-based water-in-CO2microemulsions.38A low polarity environment in fluorous surfactant F-53B based water-in-CO2microemulsions has also been found.39UV-Vis measurements are frequently used to characterize the solubilization of metal salts or biochemical compounds. Aqueous acidified K2Cr2O7has been found to be completely soluble in water-in-CO2microemulsion by UV-Vis spectroscopy.36Han and co-workers employed UV-Vis spectroscopy to monitor the extraction of trypsin solubilized in AOT/decane/water reverse micelles into compressed CO2.40Recently, microemulsions have been used in the preparation and processing of various materials.41–46In the production of metal or semiconductor nanomaterials, water-in-oil microemulsions act as aqueous micro-reactors to dissolve metal salts. One major limitation to the broader use of ILs is their inability to dissolve a number of chemicals including some hydrophilic substances. In order to extend

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