| A microemulsion is defined as an optically isotropic, transparent, and thermodynamically stable dispersion formed by two or more immiscible liquids containing appropriate amounts of surfactants and possibly cosurfactants. Generally, it is believed that surfactants are necessary components for stabilizing a microemulsion. However, Smith et al. reported an oil-continuous (water-in-oil, W/O) microemulsion composed of hexane,2-propanol and water, without surfactant, in1977wich were considered as surfactant-free (or detergentless) microemulsion (SFME). As we known, the traditional microemulsion (containing surfactant microemulsion) has three types, namely, W/O, bicontinuous (BC) and oil in water (O/W). Recently, room temperature ionic liquids (IL) have been studied extensively as green solvents, and have been reported to be used for the preparation of IL-in-IL microemulsion, but whether could be used in preparation of SFME is a valuable research topic. In addition, the traditional microemulsion has been widely used in inorganic nanomaterials, and it is necessary to study the application of IL-in-IL(IL/IL) SFME for synthesis of nanomaterials.In this paper, the phase behavior of a ternary system consisting of1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), a hydrophobic ionic liquid, propylammonium acetate (PAA), a hydrophilic ionic liquid and amphi-solvent (DMF) was investigated, and the microstructures of the microemulsion system were characterized. SiO2nanoparticles were synthesized in bmimPF6/DMF/K2O IL-SFME. And result showed that the morphologies of SiO>2were significantly affected by the SFME type and the reaction conditions.These works may lead us to get a better insight into the SFME and provide the basis for applications in nanomaterials preparation.The main contents and conclusions of this paper are summarized as follows:1) The phase behavior of the ternary system consisting of1-butyl-3-methylimid-azolium hexafluorophosphate (bmimPF6), a hydrophobic ionic liquid (IL), DMF and water was investigated, showing that there were a single-phase region which was confirmed as microemulsion by freeze-fracture transmission electron microscopy observations and a multiphase region in the ternary phase diagram. The microstructures and structural transitions of the microemulsion system were investigated by cyclic voltammetry and electrical conductivity techniques, respectively. It was found that the microemulsions could exhibit water-in-bmimPF6(W/IL), bicontinuous (BC), and bmimPF6-in-water (IL/W) microstructures, similar to traditional surfactant-based microemulsion systems.2) SiO2nanoparticles were synthesized in bmimPF6/DMF/H2O microemulsion, and the effect of microemulsion type, acid(or alkali) catalyst on the morphologies of SiO2were investigated. Results showed that SiO2nanoshperes with smooth surface canbe obtained in IL/W and BC microemulsion using HC1as catalyst. Especially, composite particles with small spherical particles bonded to large spherical particles were obtained in higher concentration of HC1.3) The phase behavior of bmimPF6/DMF/PAA ternary system was investigated. Single-phase regions and multiphase regions were observed in the ternary phase diagram and the single-phase region was confirmed as microemulsion by transmission electron microscope with negative staining observations, showing that IL-IL microemulsion can forme without surfanctant. The microstructures and the sturctural transitions of the bmimPF6/DMF/PAA SFME microemulsion system were examined by cyclic voltammetry, elecctrical conductivity and UV-visible spectroscopy techniques. It was found that the microemulsion could exhibit PAA-in-bmimPF6(IL/IL), bicontinous(BC), and bmimPF6-in-PAA(IL/IL) microstructures, similar to traditional surfactant-based microemulsion systems. |
PDF Full Text Request