非水质子性溶剂中gemini表面活性剂双液相的构建及机理研究

Gemini surfactants can self-assemble into various aggregates in water due to their unique molecular structure. During our research on the aggregation behaviors of gemini surfactants in ionic liquids, the two micellar phases coexisted in a wide temperature and concentration range, which was rarely observed in the surfactant/ionic liquid binary system. For this motivation, the aggregation behaviors of gemini surfactants in protic solvents will be investigated and nonaqueous two-phase systems will be fabricated in this project. The morphologies and structures of aggregates in two phases will be studied by the freeze fracture transmission electron microscope and small angle scattering techniques, while the mechanism for the formation of nonaqueous two-phase systems will be explored with the help of surface tension and microcalorimetry measurements and mesoscopic molecular simulation. The effects of molecular structure of gemini surfactants and properties of solvents will be investigated. The obtained results will help to understand the formation mechanism of two-phase systems and widen their applications.

Gemini表面活性剂由于其独特的分子结构，在水体系具有丰富的聚集行为。前期研究表明，通过分子结构微调，此类分子可在离子液体中形成罕见的非水双液相体系。本项目在此基础上，深入研究gemini表面活性剂在非水质子性溶剂中的聚集行为，并建立构建双液相体系的普适方法。通过冷冻刻蚀和小角散射技术研究两相中聚集体的形貌和结构；通过表面热力学和微量热方法，辅以介观分子模拟，研究双液相形成的机理。本项目将探索表面活性剂分子结构及溶剂性质对双液相形成的影响，其实施有助于更好地理解双液相的形成机理并拓展其应用范围。

非水体系双液相的构建有助于理解表面活性剂体系相分离机理，扩展双液相的应用范围。本项目研究了表面活性剂在多种非水溶剂中的聚集行为，并尝试通过调控表面活性剂和溶剂的分子结构来构建双液相。通过小角X射线散射、偏光显微镜、流变学、冷冻刻蚀电子显微镜、表面张力等表征手段，探索了各种因素对聚集体结构的影响。在质子性离子液体中，通过改变双子表面活性剂的结构（烷基链长及联接基团长度）调控其聚集行为，提升表面活性剂的疏溶剂作用，有利于双液相的形成；而增加离子液体中烷基链的长度导致溶剂内聚能不足，不利于双液相的形成。选取单链表面活性剂，探索非质子性离子液体和低共熔溶剂的结构对聚集行为影响。对于咪唑类非质子性离子液体，增加阳离子烷基链长，使其溶剂作用变弱而助表面活性剂作用变强，这反而使得表面活性剂在其中表现出更丰富的相行为。低共熔溶剂具有较大的内聚能，表面活性剂在其中表现出优于离子液体中的聚集行为；氢键供体和受体在自组装过程中表现出不同的作用，这使得低共熔溶剂的可调控性更强。本项目拓展了表面活性剂在非水体系中的聚集行为，尤其是在非质子性离子液体以及新兴的低共熔溶剂，为非水体系双液相的构建提供了新思路。