| Ionic liquids (ILs) are receiving great attention as a class of neoteric solvents because of their special physical and chemical properties, such as low volatility. high thermal stability and designable property. In recent years, the microemulsions containing ILs have become an interesting topic. It revealed that ILs can act as effective additives to modify the properties of microemulsions, which expands the utilization of microemulsions. Meanwhile, the application of ILs is also expanded. Based on the previous studies by other groups, the properties of nonaqueous microemulsions, which use ILs as polar phase, was investigated in this dissertation. Also, using the mixture of an IL and nonaqueous polar solvents instead of pure IL to form ionic liquid microemulsions had been described. Additionally, the effect of ILs on the traditional water-based microemulsions was investigated. The contents of this dissertation are as follows:1. The properties of IL microemulsions were investigated in detail. Firstly, the solubilizations of ILs in polyoxyethylene tert-octylphenyl ether surfactants systems were studied. It indicated that the IL which had higher hydrogen-bond basicity, longer alkyl chain length of cation, possessed a higher solubilization. On the basis of these results, the phase behavior of the1-ethyl-3-methylimidazolium acetate (emimCHbCOO), polyoxyethylene tert-octylphenyl ether (TX-45) and cyclohexane system at25℃was studied. And, microregions of emimCH3COO-in-cyclohexane (IL/O), bicontinuous and cyclohexane-in-emimCH3COO (O/IL) were identified by electrical conductivity measurements. The experiments of droplet size revealed the formation of the IL microemulsions. The micropolarities of the emimCH3COO-in-cyclohexane microemulsions were investigated by the UV-vis spectroscopy using methyl orange (MO) and methylene blue (MB) as absorption probes. The results showed that, with the addition of IL, the polarity of the microemulsions was increased, but it didn’t change any more when the IL pools began to form. Moreover, the study of spectroscopy also indicated that biological molecule riboflavin and metal salts such as CoCl2, CuCl2could be solubilized into the microemulsions droplets. Conductivity measurements indicated that the microemulsions didn’t have temperature-induced percolation, which showed very low activation energy. However, the systems possessed volume-induced percolation, which could be assisted by the metal salt CuCl2and polyethylene glycol400.2. The formation of nonaqueous microemulsions containing the mixture of IL and polar solvent as the polar phase was studied. The phase behavior of the bmimCl, polar solvent (formamide or ethylene glycol), polyoxyethylene tert-octylphenyl ether (TX-100) and cyclohexane system at25℃was investigated. Electrical conductivity measurement was used to identify the three microregions of the nonaqueous microemulsions. Dynamic light scattering (DLS) studies revealed that the droplet size of reverse microemulsions of bmimCl-polar solvent in cyclohexane increased linear with the increase of the polar phase-to-TX-100molar ratio, which confirmed the formation of reverse microemulsions. FTIR spectra showed that there were hydrogen-bond interactions between the mixed polar phase and the surfactant. The interactions might be the driving force for solubilizing polar phase into the microemulsions. The polarity of these microemulsions was increased with the increasing amount of polar phase, which was different from the microemulsions containing IL as the only polar phase. The polarity was dependent of the polar phase-to-TX-100molar ratio (R), and nearly independent of the surfactant concentration. UV-vis studies indicated that the nonaqueous reverse microemulsions could dissolve metal salt CoCl2and biological molecule riboflavin.3. A study was carried out concerning the effects of ILs (bmimBF4and bmimCl) on the properties of nonionic surfactant-based H2O/TX-100/hexanol/cyclohexane microemulsions at25℃. Several properties of microemulsions, such as polarity, conductivity, viscosity and droplet size, were investigated. With the addition of IL, the polarity of the microemulsions was increased, and the water needed to form water pool was decreased. Conductivity results revealed that the onset water content of electrical percolation was decreased with the presence of IL and continued to decrease as the amount of IL increased. The viscosity of microemulsions was increased with the increasing amount of IL. The influence of bmimBF4on the properties of microemulsions was greater than bmimCl. The measurement of droplet sizes of microemulsions indicated that the bmimBF4was almost all solubilized into the polar core of microemulsions, but the bmimCl wasn’t. This explained the difference of the two IL’s effect on the properties of microemulsions.4. The effects of ILs on temperature-induced and volume-induced percolation as well as water solubilization capacity of anionic surfactant AOT-based microemulsions were investigated. The temperature-induced percolation phenomena of microemulsions were delayed with the addition of IL. And the percolation temperature threshold (Tp) of microemulsions was increased with an increase of the IL’s concentration. The alkyl chain length, hydrogen-bond acidity and end group of cation had great effect on the Tp. However. Tp was slightly affected by the ILs anions. The viscosity and droplet size of microemulsions were all decreased when addition of ILs and the observed decrease correlated roughly with an increase in Tp. The volume-induced percolation phenomena of microemulsions were also delayed by the ILs. The volume percolation threshold (Φp) was increased in the presence of IL, and increased with the increase of the concentration of IL at low IL’s concentration, whereas no percolation phenomena could be observed at high IL’s concentration. The Φp value was increased with increasing chain length of ILs under the same conditions. Additionally. the water solubilization capacity was enhanced as function of IL concentration at low concentration of IL. reached a maximum and decreased for high IL’s concentration. For the microemulsions, the water solubilization capacity was increased with the increase of chain length of ILs at low IL’s concentration. |
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