| The environmental responsive ionic liquids(ILs)refer to the‘intelligent'liquids that can change their structure and properties under external stimulus.The environmental responsive aqueous two phase systems(ATPSs)are kinds of liquid-liquid two phase systems which could be regulated by external stimulus.Common stimulation methods include changing the temperature and p H of the system,applying light,electric and magnetic fields,etc.Among them,light irradiation has been widely concerned because of its advantages of easy operation,mild conditions and no introduction of other substances.The ATPSs constructed by ionic liquid has the unique properties of adjustable structure of anion and cation of the ionic liquids,short equilibrium time and non-emulsification,thus such systems have a good application prospect in the fields of extraction separation and enrichment of biological materials.However,the current studies on the environmental responsive of ionic liquid ATPSs are mostly temperature and p H responsive systems.The study of photo-responsive ionic liquid ATPS has not been reported so far.In this context,13 cinnamic acid-based and 5 azobenzene-based photo-responsive ionic liquids were designed and synthesized in this work.Then the thermal properties and the photoisomerism in aqueous solution were determined in detail.Azobenzene-based ionic liquids and inorganic salts were construct a series of photo-responsive ATPSs for the first time.Interestingly,the liquid-liquid phase behavior of the ATPSs could be regulated by alternatively UV and visible light irradiation.The phase forming ability of these ionic liquids and the mechanism of UV/vis light reversible switchable behavior of ATPS were investigated systematically.Based on the unique light-responsive phase behavior of the ATPSs,a highly efficient and selective Aza-Michael reaction was achieved with ATPS as the reaction medium.The homogeneous reaction,heterogeneous separation and ATPS compositions reused were realized.The main contents are as follows:1.13 kinds of cinnamic acid-based ionic liquids,including[Cinn-Cn-MIM][Br](n=4,6,8),[Cinn-Cn-DMEA][Br](n=4,6,8),[Cinn-Cn-TMA][Br](n=4,6,8),[Cinn-C8-DMEA][BF4],[Cinn-C8-DMEA][Tf2N],[Cinn-C8-DMEA][N(CN)2],[Cinn-C8-DMEA][CF3SO3]and 5 kinds of azobenzene-based ionic liquids,including[C2Azo C4MIM][Br],[C4Azo C2TMA][Br],[C4Azo C2MIM][Br],[C4Azo C2DMEA][Br]and[C4Azo C4MIM][Br]were synthesized.The melting point and thermal decomposition temperature of them were characterized by differential scanning calorimeter and thermogravimetric analyzer.The influence of ionic liquid structure on melting point was analyzed.The photo-responsive property of ionic liquids in aqueous solution with different chemical structure was determined by UV/vis irradiation absorption spectroscopy.2.Using the synthesized ionic liquid and inorganic salts,a series of photo-responsive ionic liquid ATPSs are formed and the binodal curves of the systems were measured in detail.Factors affect the liquid-liquid phase equilibrium of ATPSs,such as chemical structure of IL,type of the salts and UV irradiation were discussed in detail.Then,mechanism of formation and liquid-liquid phase behavior regulation were investigated by dynamic light scattering(DLS),small-angle X-ray scattering(SAXS),cryogenic transmission electron microscopy(Cryo-TEM).It is found that phase forming ability of the IL is in accordance with the hydrophobicity of azobenzene-based ILs,IL with a more hydrophobic property is easier to form an ATPS under the same condition.Light switchable behavior of ATPS is attributed to the light regulated micelles of IL in the systems.3.On the basis of investigation the effects of ionic liquids dosage,reaction time,reaction temperature,substrate molar ratio and other factors on the yield of double addition products,the optimal reaction conditions were obtained.Based on the characteristics of ATPSs that can be changed into a homogeneous system by UV irradiation,and then induced phase separation by vis-light irradiation,the Aza-Michael reaction at room temperature was performed which used ATPS as the medium for the first time and the reaction yield can reach 99%.At the same time,,the homogeneous reaction,heterogeneous separation and the system component recycling were realized by using UV/vis light irradiation to reversibly regulate the liquid-liquid equilibrium in ATPSs.After 5 cycles of the system,the product yield still remained above95%.These studies have expanded the application range of ATPSs and provided a new green medium for chemical reaction. |
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