功能离子液体物理化学性质的实验测定和粗粒极化模型理论研究

Recently, interest has tremendously increased in the task-specific ionic liquids (TSILs) with carboxyl and amide groups, which have been widely considered as environmentally friendly materials due to their biodegradability and reduced toxicity. Although the existence of local heterogeneous environments in TSILs has been received much attention, knowledge about static structures and dynamic changes of free volume and aggregation in TSILs is a requisite for understanding the TSILs properties.In this project, we combine the application of experiments, theoretical model, and molecular dynamics (MD), which has proven to be a useful approach to explore the structure-property relationship of TSILs. First, a new electronically polarizable model, CG-EEM, is developed for the TSILs, based on the combination of the group electronegativity equalization and coarse-grained methods. CG-EEM computes the explicit charges of groups, which are fluctuating with functional groups and different external potential. And due to the enhancing short-range and screening long-rang electrostatic interactions, the parameters of the CG-EEM model are fitted not only by the QM results but by fully considering the experimental properties of liquid-phase TSILs. The density, radial distribution function, diffusion constant, time correlation function are clearly described.Second, the amine and carboxyl TSILs are prepared, which are characterized by H1 NMR spectroscopy, different scanning calorimetry (DSC), etc. The values of density, surface tension, conductivity, and vaporization enthalpies are measured by the standard addition method (SAM) and the isothermal TGA methodology. We then estimate the thermal expansion coefficient, solubility parameter, and iconicity of the TSILs. Finally, by the results of experiments and MD results, the quantitative structure-property relationship of TSILs with carboxyl and amide groups has been clearly understood and supported, the heterogeneity of TSILs is characterized, the theoretical nature of free volume and aggregation on properties has been validated, and so on. Our study is aimed to broaden the TSILs's applications in the areas of gas capture, biomaterials dissolution, reaction medium, and this is most encouraging.

氨基和羧基功能离子液体(TSILs)具有生物再生性能，是新一代环境友好性的离子液体。目前，尽管人们已熟知离子液体周围环境的各向异性，但对其内部"自由体积"和团簇/聚集体等的静态结构及动态变化的研究还十分有限。本项目采用实验和理论模拟紧密结合的方法，首次将基团电负性均衡方法与粗粒模型相结合，建立新型粗粒极化电荷模型CG-EEM；探讨外场变化对TSILs粗粒电荷分布的动态影响，利用拟合方程描述短程、长程静电作用；准确模拟TSILs的性质，空间结构、团簇/聚集体的时间相关函数等。实验上合成、表征氨基和羧基TSILs，测其精准物理化学性质，考察热膨胀系数、溶解度参数，离子率等。最后全方位综合实验和理论结果，深入理解TSILs结构与性质关系，探讨"自由体积"、团簇/聚集体静态结构和动态变化，及其对TSILs性质影响的理论本质等。拓宽TSILs在气体吸收、生物质溶解、反应介质等方面的应用。

设计和开发具有各种物理化学性质的新型功能材料是发展新材料的一个重要手段，离子液体（ILs）是近十几年来发展迅速的新型功能材料和绿色溶剂，不仅在替代传统溶剂方面表现出优异的应用前景，在气体吸附分离、电化学、生物质溶解、催化剂负载等方面的应用也引起研究者广泛的兴趣。本项目采用实验和理论的方法研究了一系列功能离子液体（TSILs）的热力学性质和构效关系、构建了粗粒极化电荷模型CG-EEM，并将其逐步应用于气体吸附机制的探讨。首先，采用改变阴阳离子、多元混合等方法设计合成了一系列TSILs，实验上精确测定其物理化学性质，考察电导率、电导活化能和粘流活化吉布斯自由能等动力学性质，提出了预测TSILs极性的新方法；给出TSILs阴阳离子等张比容新概念；利用Born-Harber（BH）循环计算TSILs热力学性质等。其次，利用空隙理论、分子内禀边界轮廓模型、离子/分子聚集状态的统计分析等方法揭示了在离子液体微观存在的“自由体积”对宏观性质影响的本质；结合动态光散射、标准加入法以及分子动力学模拟结果，考察了多元体系TSILs纳微结构及其形成机制，首次给出多元离子液体体系“复盐”的精确结构组成。再次，将基团电负性均衡模型EEM和Voth教授建立发展的粗粒模型CG相结合，建立粗粒极化电荷模型CG-EEM。充分考察其短程和长程静电相互作用，利用Force Matching（FM）方法拟合粗粒电负性、硬度、非键相互作用等力场参数，编写程序。计算得到的结构性质表明，CG-EEM模型给出了与已有实验结果符合非常好的微观结构，尤其是分子间的相互作用。最后，将TSILs负载到金属有机骨架材料（MOF），通过电荷差分、弱相互作用、轨道分析等研究CO2的吸附机理，为将离子液体应用于气体吸附、催化剂载体等提供理论基础。依托该项目，我们发表了13篇SCI论文，其中影响因子大于3.0的高质量论文4篇，培养博士生1名、研究生4名。项目负责人和参与者多次参加国内外学术会议，负责人到美国芝加哥大学化学系访学研究一年，并建立了长期的合作与交流。本项目在执行期间顺利完成了预期研究目标。