Charcterization of the nature of interactions in ionic liquid co-solvent mixtures by dynamic light scattering (DLS)

在埃尔兰根的SAOT和LTT目前的研究活动中，来自大量流体的动态光散射（DLS）以及DLS在流体表面的应用，也称为表面光散射（SLS），已成功地用于表征纯离子液体（ILs）及其与共溶剂的混合物。除了为建立可靠的数据库做出重要贡献外，DLS对宏观热物性的测定还提供了对IL共溶剂混合物相边界处的体结构和流体结构的深入了解。在这方面，应该继续和扩大已经属于DFG优先方案“离子液体”（SPP 1191）第二供资期的研究活动。进一步选择具有强氢键倾向的咪唑基il和助溶剂，应采用DLS和/或SLS进行研究。通过接触角测量的实验方法的扩展将允许更详细地分析存在于IL共溶剂混合物相边界的分子相互作用。对于大量流体的DLS，所有可能的IL共溶剂混合物的扩散模式都应该通过研究大范围散射矢量或波矢量上的散射光来确定。对于SLS，在宽波矢范围内散射光的研究应指出烷基链长度对表面模式阻尼的影响。因此，关于液体表面结构的信息是可获得的，例如，以阳离子的烷基链取向的形式。

Within current research activities at SAOT and LTT in Erlangen, dynamic light scattering (DLS) from the bulk of fluids and the application of DLS to fluid surfaces, also called surface light scattering (SLS), is successfully used for the characterization of pure ionic liquids (ILs) as well as their mixtures with co-solvents. Besides offering a significant contribution to a reliable database, the determination of macroscopic thermophysical properties by DLS also provides a close insight into the bulk structure and the fluid structure at the phase boundary of IL co-solvent mixtures. Here, research activities which were already part of the second funding period of the DFG priority program “Ionic Liquids” (SPP 1191) should be continued and extended. Further selected imidazolium-based ILs and co-solvents which in particular show the tendency to strong hydrogen bonding should be investigated by DLS and/or SLS. An extension of the experimental methodology by contact angle measurements will allow a more detailed analysis of the molecular interactions present at the phase boundary of IL cosolvent mixtures. For DLS from bulk of fluids, all diffusion modes conceivable for IL cosolvent mixtures should be identified by the investigation of the scattered light over a wide range of scattering vectors or wave vectors. For SLS, the study of the scattered light over a wide range of wave vectors should point out the influence of the alkyl chain length on the damping of surface modes. Thus, information on the structure at the liquid surface is accessible, e.g., in form of the orientation of the alkyl chain of the cation.