Preparation, Properties And Application Of Imidazolium Ionic Liquids

In recent years Ionic Liquids(ILs)have been successfully applied in many scientific fields such as organic synthesis, separation and purification, catalytic chemistry, electrochemical and nano-materials due to their peculiar properties such as very low vapor pressure at normal temperature, low melting point, nonvolatile, nonflammable, wide liquid range, high thermal stability, large electrochemical windows, good solubility. Dialkyl imidazolium ionic liquids are a kind of the most concerned ILs for the more stable physicochemical properties, smaller viscous, larger electrochemical windows. But their industrial applications are limited because the synthesis processes are complicated, the production cost are expensive. Magnetotheological (MR) fluid is a prospective smart fluid which is typically made by suspending spherical micron-sized magnetic particles (e.g.iron microspheres) in a carrier fluid such as silicone oil or water. The primary reason for selecting an ionic fluid as carrier liquid is that it has a relatively low melting point and high decomposition temperature, possesses non-vapour pressure and has proper viscosity. Hence, the ionic liquid may be used in high-vacuum systems and wide temperature field.The imidazolium ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM] BF4) was synthesized using N-methylimidazole, ethyl bromide and tetrafluoroboric acid by two steps. IR showed that the product had the characteristics of functional groups of [EMIM] BF4 in 1170 cm-1, NMR spectroscopy confirmed the basic structure of the products as the ionic liquid [EMIM] BF4. The TG and DSC showed that [EMIM] BF4 had the start decomposition temperature at 245℃and themal decomposition temperature at 472.5℃, glass transition temperature at-91.3℃, which indicated that it owned good themal stability and low glass transition temperature. The electrochemical window of [EMIM] BF4 was broad from the result of the electrochemical analysis. The productivity of [EMIM] BF4 reached 88% by improving process and reducing the cost while shortening time for 2 days.The imidazolium ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES), was synthesized using N-methylimidazole and diethyl sulfate by one step. IR showed that the product had the characteristics of functional groups of EMIES in 1171 cm-1'NMR spectroscopy confirmed the basic structure of the products as the ionic liquid EMIES.The TG and DSC showed that EMIES had the start decomposition temperature at about 300℃and themal decomposition temperature at 365.2℃,glass transition temperature at-70.4℃,which demonstrated that it had good themal stability and low glass transition temperature. The electrochemical window of EMIES was broad from the result of the electrochemical analysis. The reaction process was simpler by improvement.The productivity of EMIES reached 90%.A new magnetorheological (MR) fluid by dispersing carbonyl iron powders (CIPs) and surfactant in the ionic liquids EMIES synthetized in this paper were prepared. The Vibratinig Sample Magnetometer results that the saturation magnetization is 166.4emu/g, the coercivity is 15.27Oe and the residual magnetization is 0.7992emu/g, which give MR fluid an excellent soft magnetic properties. Sedimentation stabilities show that the sedimentation ratio is 25%. Magnetotheological properties of the MR fluids were characterized, which show that the off-state field viscosity of the prepared MR fluid is lower than the non-PEG MR fluid in the same volume fraction while the shear stress is higher and the magnetic-response time is short, about 0.1 seconds.