离子液体微乳液的光散射和界面流变性质研究

Ionic liquid(IL) has the advantages of low volatility,low melting point and high chemical and thermal stability,.but  it also has the shortages of high viscosity, high cost and poor solubility of some compounds.  The ionic liquids microemulsion(ILs) can overcome these shortcomings.In the past, many researchers were mainly focus on the study of ILs thermodynamic equilibrium properties by phase diagram, surface tension,IR,FS, SAXS and NMR methods. Dynamic light scattering(DLS) was also applied to the research of ILs, but mainly used to determine the particle size of dispersed phase. In this program, three-dimensional dynamic/static light scattering technology and optical micro rheological technology developed in recent years will be used to the investigation of DLS properties (droplet size, diffusion coefficient, the second willy coefficient and shape factor, etc.) and interfacial rheological properties (interfacial viscosity, storage modulus G ', loss modulus G ", relaxation time, etc.)of ILs. The influence of some factors such as ionic liquid, surface active agent, surfactant, oil phase and temperature on the DLS and rheological properties, and the interactions between each ingredient of ILS, as well as the correlation between DLS properties, rheological properties and microemulsion(or micelle) geometry transition of microemulsion formation process (or phase change process) will be investigated, respectively. On the basis, the formation mechanism of ILs will also be discussed. The purpose of this research project is to provide a new understanding for ILs.

离子液体具有难挥发、熔点低、稳定性好等优点，但粘度大、成本高、对一些化合物溶解性差。将离子液体制成微乳液，可以在一定程度上克服其缺点。过去人们主要通过相图、表面张力、红外、荧光、小角 X 射线散射、核磁共振等手段研究其性质，动态光散射技术也应用于离子液体微乳液的研究，但主要是测定微乳液分散相的粒径。本课题利用三维动/静态光散射技术和近年来发展起来的光学微流变技术对离子液体微乳液的光散射性质（液滴大小，扩散系数，第二维利系数，形状因子等）和界面流变性质（界面粘度、储存模量G'和损耗模量G"、弛豫时间等）进行研究，考察离子液体、表面活性剂、助表面活性剂、油相以及温度等因素对体系光散射性质和界面流变性质的影响，研究离子液体微乳液组分间相互作用以及微乳液形成过程（相变过程）的光散射性质和界面流变性与微乳液结构转变的关系，探讨离子液体微乳液的形成机理，为离子液体微乳液的研究提供新的认识。

离子液体微乳液(ionic liquid micoemulsion,ILs)可在一定程度克服粘度大、极性强、对有机物的溶解度有限等缺点。研究ILs的胶体和流变性质对于了解其形成机理及其应用具有重要意义。.本项目采用动态光散射(DLS)和扩散波谱（DWS）法研究了离子液体微乳液的胶体性质（如微乳液滴大小、扩散系数、均方位移等）和微流变性质[如储能模量G'（弹性模量）、损耗模量G"（粘性模量）等]。考察的体系有离子液体作为极性相的ILs，如[Bmim]BF4/TX-10 /环己烷，[Bmim]BF4/TX-100/环己烷，[Bmim]BF4/Tween-20 /二甲苯，[Bmim]PF6//TX-10 /环己烷, [Bmim][Ms] + H2O)/(Tween 20 + n-戊醇)/n-庚烷和离子液体作为极性相的ILs如[Bmim]PF6/TX-100/H2O。主要研究成果如下：（1）微乳液滴大小随着离子液体和表面活性剂质量分数的增大而增大，微乳液滴流体力学半径Rh与微乳液滴结构有关，在O/IL和IL/O的单相区，Rh=1.64~40.6nm，而在双连续相区，Rh=597~4570nm。粒径的动态光散射测量结果证明了微乳液双连续相结构（管状结构）的存在。（2）均方位移MSD.（<∆r2>）、扩散系数D与液滴粒径大小成反比；MSD随着油相质量分数的增大和弛豫时间的增加而增大，均方位移与弛豫时间τ具有幂函数关系<∆r2>~τα（α为幂指数，α=0.87~0.1.33，α值与微乳液组成有关，下同）。（3）离子液体微乳液的G'非常小，G"远大于G'，表明离子液体微乳液是一种纯粘性流体。G"与频率ω也具有幂函数关系G"~ωα（α为幂指数，α=0.86~1.35），表明微乳液体系具有亚扩散或超扩散行为。DLS和DWS综合研究表明，离子液体微乳液存在由O/IL-双连续结构-IL/O的结构相转变，具有近似于牛顿流体的流变行为。