The Regulation Of Phase Behavior Of Mixtures Of Bis(Trifluoromethane Sulfonimide) Based Ionic Liquids And Water By Some Additives

Ionic liquids (ILs) are organic salts, and they are liquids at ambient conditions. Due to their uniqueproperties, such as negligible vapor pressure, high thermal and chemical stability, and strong solubilityability for inorganic and organic species, ILs have used as “green solvents” to replace traditional VOCs inorganic synthesis and catalysis. Some ILs can be partially miscible with water to form two-phase systems,and these systems have a wide range of applications in materials synthesis, extraction and separation ofbiomolecules. However, partially miscible IL+water systems reported up to now often have a highmiscible temperature which restricts the application of such systems. As a part of the project supported bythe National Natural Science Foundation of China (No.21133009), the effect of some molecular solventsand inorganic salts on the liquid-liquid equilibrium of bis(trifluoromethane sulfonimide) based ILs andwater was investigated. The impact of temperature and the additives on the microstructure of IL+waterwas also investigated by DLS and NMR. The main contents of this work are as follows.1. Five kinds of bis(trifluoromethane sulfonimide) based ILs have been systhesised and characterized by1H NMR. The liquid-liquid equilibrium phase diagrams of [ValC2][Tf2N]+water,[Choline][Tf2N]+water,[Betaine][Tf2N]+water,[Girards][Tf2N]+water, and [Carnitine][Tf2N]+water were determinedexperimentally.2. The effects of organic additives (ethanol, acetonitrile, ethylene glycol, glycerol, PEG200, dimethylformamide, dimethylsulfoxide) on the phase diagrams of ILs+water systems were investigated, and thestructural effects of the organic additives and their amount on the equilibrium phase diagrams wereexamined in detail. The results show that the organic additives could reduce the temperature of the ILs+water systems except glycerol.3. The effects of inorganic salt additives (NaF, NaCl, NaBr, NaI, NaNO3, NaBF4, NaCH3COO, NaSCN,Na2CO3, Na2SO4, Na3PO4) on the liquid-liquid equilibrium of [Girards][Tf2N]+water and[Carnitine][Tf2N]+water mixtures were investigated, and the sensitivity of critical solution temperature onthe type and amount of inorganic salt additives were assessed. The results show that the structure of the ILs and the type of the salts have great effect on the temperature of the ILs+water systems, the salt whichhas salting-out property chould enhance the temperature of the systems.4. The impact of temperature and the additives (ethanol, glycerol) on the microstructure of[Girards][Tf2N]+water,[Betaine][Tf2N]+water was investigated by DLS and NMR, and the resultsshowed that interactions between the additive and the IL is the main factor to affect the microstructure ofILs+water systems. The results show that some aggregates exist in the systems, and temperature of thesystems has great effect on the size of the aggregates. The addition of ethanol could deduce the size of theaggregates, inverse,the addition of glycerol could enhance the size of the aggregates.