离子液体水溶液的下临界溶解温度相行为研究

Lower critical solution temperature (LCST) -type phase separation has been found only in a few mixtures of ionic liquid (IL) and water at ambient temperature. An effective control and use of this kind of phase separation are very important to facilitate the application of ILs in catalysis, separation and nano-materials preparation. However, the mechanisms and regulation rules for the LCST-type phase separation in IL / water mixtures are not clear up to now, which will greatly limit the development and application of such ILs aqueous solutions. In this project, we are going to design and synthesize of a series of functional ILs, and the mechanisms of LCST-type phase separation and microstructure in the IL/water mixtures will be investigated by combined methods of thermodynamic (such as phase equilibria), spectroscopy (Dynamic light scattering, NMR, IR and Raman) and molecular simulation (quantum chemistry calculation and molecular dynamic simulation). The effect of cationic structure, anionic type, and functional group property of the ILs on solution structures and phase behavior will be systematically examined, and relationship between solution structures and phase behavior will be established. The nature for the interactions between ILs and water and the dominant driven force for the LCST-type phase separation in IL / water mixtures will be illustrated at atom/molecule level. The results are expected to provide new insights for the application of ILs in extraction, separation and catalytic reaction.

目前，已发现极少数离子液体的水溶液在室温附近表现出下临界溶解温度(LCST)的相行为，有效地调控这种温度响应特性，对于拓展离子液体在催化、分离、纳米材料制备等领域的应用具有重要意义。但是，关于离子液体水溶液的LCST相行为的作用机制及调控规律仍不清楚，这在很大程度上限制了这类离子液体的发展与应用。本项目拟在设计、合成离子液体的基础上，将相平衡等热力学方法与动态光散射、IR、NMR等谱学技术及分子模拟方法相结合，深入系统地研究阳离子的结构、阴离子的种类、官能团的特性对离子液体水溶液微观结构和LCST相行为的影响规律，建立离子液体溶液微观结构-LCST相行为之间的构效关系；从分子/原子水平上揭示离子液体与水分子相互作用的本质，确定产生LCST特殊相行为的主要驱动力，阐明离子液体LCST特殊相行为的微观形成机理，为离子液体在萃取分离及催化等方面的应用提供科学依据。

目前仅有少数离子液体被发现在水中表现出下临界溶解温度(LCST)的相行为，有效地调控这种温度响应特性，对于拓展离子液体在催化、分离、纳米材料制备等领域的应用具有重要意义。本项目设计、合成了一系列具有LCST的咪唑类、膦类、胺类和胆碱类等4类离子液体，较系统地研究了阳离子结构、阴离子种类、官能团的特性等因素对离子液体溶液的微观结构及相行为的影响规律。在实验结果的基础上，采用分子模拟和谱学的方法研究了离子液体阴阳离子之间的相互作用及LCST相行为形成机理，揭示了阴离子与水的氢键相互作用是产生LCST相行为的主要驱动力。根据微观作用机制，我们又设计了一系列具有LCST的混合离子液体体系，并进行了实验验证。此外，我们还初步探索了功能化离子液体作为溶剂在CO2转化方面的应用。 综上所述，本项目的开展，建立了离子液体溶液微观结构-LCST相行为之间的构效关系，为离子液体在分离及催化等方面的应用提供了科学的指导。