| Ionic liquid?IL?-water two-phase systems are environmentally benign liquid-liquid two-phase systems and have a promising application prospect in many areas,such as extraction separation,biotransformation,reaction catalysis and so on.However,current IL-water two-phase systems have problems such as poor phase separation,limited interactions with solutes,restricted extraction performance,et al.Based on the unique property of ILs that task-specific tunability,a series of novel functionalized IL-water two-phase systems were constructed in this dissertation via modifying the structures of ILs to enhance the hydrogen-bond?H-bond?basicity and control the aggregation behavior.The connection between the phase equilibriums and the molecular structures as well as the microscopic aggregation of the corresponding was systematically studied.Also the application performance of the constructed systems,including the extraction for representative bio-active compounds,the solubilizing for hydrophobic drugs and the dispersing for nano-materials,were evaluated.A family of novel aqueous biphasic systems?ABSs?based on cholinium long-chain carboxylate ILs?LCC-ILs?were constructed by introducing carboxylate anions with long alkyl chain to cholinium ILs.The effects of the phase compositions,H-bond basicity,and ILs' aggregation on the phase equilibrium and extraction performance of the LCC-IL-based ABSs,indicating that the extension of the alkyl chain on the IL anion enhances the phase splitting ability of the ILs and increases the H-bond basicity of the IL-rich phases.And distinct liquid crystal structures were found when carbon number of the IL anion was equal to or greater than 8.Furthermore,the LCC-IL-based ABSs presented excellent extraction ability for tryptophan,phenylalanine and caffeine.The partition coefficients of the solutes reached up to 120,58.5 and 120,respectively,which increase with the extension of the alkyl chain on the IL anion as well and profoundly higher than those in conventional IL-based ABSs.A family of polymeric ionic liquid?PIL?-based ABSs were constructed by introducing PILs with high molecular weights to promote phase separation.The phase equilibriums of the ABSs composed of different PIL and salting-out agent combinations were determined.And the effect brought by differences of polymerization methods,train lengths,molecular weights and anions species of the PILs were systematically studied.Also the extraction performance of the constructed PIL-based ABSs was evaluated with different kinds of bio-active compounds,including amino acids,alkaloids,polyphenols and antibiotics.The strategy that using PILs to replace ILs was proved profoundly effective for promoting the phase splitting of ABSs.And PILs with higher molecular weights would lead to better phase splitting ability.In addition,the problem that PILs would precipitate in ABSs was efficiently solved by two approaches.One was employing carboxylate anion to enhancing the interactions between anions and water.The other was using polymerization methods such as reversible addition-fragmentation chain transfer?RAFT?polymerization to control the molecular weight of the PILs.As a result,PIL-based ABSs presented outstanding performance.Specifically,the partition coefficients of tryptophan and phenylalanine in the ABS containing poly?1-vynyl-3-butylimidazolium bromide?with a molecular weight of 7079 g·mol-1 reached up to 922.3 and 200.3,respectively,which were 25 times and 8 times as those in conventional 1-butyl-3-methylimidazolium bromide-based ABS.Based on the conclutions in the study of cholinium LCC-ILs,a family of phosphonium LCC-ILs were prepared for the first time and both the cation and anion were introduced with long alkyl chains to promote the H-bond basicity and aggregation further.The melting points/glass transition temperatures,thermal stability,viscosities,H-bond basicity values???,dipolarity/polarizability values??*?and microscopic aggregation of the phosphonium LCC-ILs were systematically characterized.IL-water lower critical solution temperature?LCST?systems based on these LCC-ILs were constructed.And the effects brought by the differences of ? structures and concentrations on the LCST systems were discussed.The experimental results indicated that the LCC-ILs presented rather strong H-bond basicity?? = 1.50?1.64,25 ??,which increased with the extension of alkyl chains on anion and cation.And the dipolarity/polarizability values of the LCC-ILs were relatively low??*= 0.77?0.8,25 ??,which led to good lipophilicity,and the ?*values decreased with the extension of alkyl chains on anion and cation.The extension of the alkyl chains also promoted the aggregation structures,leading a spatial correlation length of 13.8?19.6 A.The LCST phase transition the constructed LCST systems were very sensitive to the external temperature variation.The critical temperatures increased with the increasing of the IL concentration and were able to be tuned in a wide temperature range of 10?90 ?.In addition,the alkyl chain on the IL cation had a more significant effect on the LCST phase transition than that on the anion.Based on the excellent hydrophilicity,lipophilicity and the phase transition ability responded to the external thermal stimuli of the LCC-ILs,the solubility of the hydrophobic drugs and the dispersing ability of the nano-materials in IL-water LCST systems were studied.It was demonstrated that the solubilities?25 ??of indomethacin,metronidazole and naproxen in the LCC-IL-water LCST systems were 6?7150 folds higher than those in pure water.And the LCC-IL-water LCST systems were also bale to disperse multi-walled carbon nanotubes,graphene,Pd and Pt nanoparticle,maintained the reversible LCST phase transition function.Specifically,the LCST system based on tributyldodecylphosphonium stearate presented a high dispersing capacity(1.3 mg·mL-1,25?)for carbon nanotubes,which was 6.5-fold higher than those reported in literatures. |
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