非卤化物类双亲性烷基咪唑盐组装溶致液晶及其应用

That exploring new amphiphilic molecules with specific properties and function and their aggregates is very important for the development of colloid science and self-organization. Alkyl-substituted imidazolium salts have attracted considerable attention in the areas of catalysis, organic synthesis, electrochemistry and liquid/liquid extraction. By proper design on cationic or anionic parts, they might become amphiphilic componds with specific properties of catalysis or solvation. Ordered assemblies composed of these imidazolium salts and solvents would exhibit potential applications in many fields. However, only the long-chain alkyl-substituted imidazolium halide have successfully formed lyotropic liquid crystals (LLCs). In this project, non-halide types of alkyl-substituted imidazolium salts are to be designed and to be used to construct LLC assemblies. Influence of factors including cations, anions, molecular structure, temperature, composition and additives on the ordered aggregate will be discussed to find out the general assembling mechanism. Alkyl-substituted imidazolium halides have been proven to construct ordered aggregates successfully and easily for their strong hydrogen-bond interaction from anions. This project will focus on what kinds of imidazolium salts other than halides could construct LLCs and what kind of interaction would work during the formation of ordered structure. For this reason, non-halide types of imidazolium salts were intentionally selected. Meanwhile, expanding the types of imidazolium salts used to form ordered assemblies is valuable for that more virtues of ionic liquids could easily remain and be displayed in the new ordered aggregate.

寻求具有特定功能和性质的新型双亲分子及其构筑的有序聚集结构是聚集体化学发展的重要内容。烷基咪唑型室温离子液体在催化、有机合成、萃取分离、电化学等领域备受关注。结构的可设计性使得上述咪唑盐能够表现出双亲性，成为一类具有特定催化、溶解性能的新型表面活性物质。目前，用于组装溶致液晶的双亲性咪唑盐皆为熔点较高的长链烷基咪唑卤化物。本项目拟设计选取兼具离子液体性质和表面活性的非卤化物类烷基咪唑盐用于组装溶致液晶等有序聚集体，考察分子结构、添加剂等多种因素对有序聚集结构形态和性质的调控，探求组装规律。该研究旨在突破目前表面活性剂型咪唑盐多为卤化物的限制，重点考察非卤化物类双亲性烷基咪唑盐组装有序聚集结构的作用机制，并有望将离子液体的催化、溶解性等功能特性引入溶致液晶等有序聚集体，对于建立新型介观超分子结构、拓展组装体系类型和功能，具有重要的理论研究和应用价值。

本项目旨在考察非卤化物类双亲性烷基咪唑盐构建溶致液晶等有序聚集结构的组装行为和作用规律。通过选取一系列不同类型的1-烷基-3-甲基咪唑盐[CnMim]X（X=Cl、BF4、PF6、NO3、CH3COO、OTf、NTf2 ; n=6、8、10、12），成功地在1-烷基-3-甲基咪唑硝酸盐[CnMim]NO3和乙酸盐[CnMim]CH3COO的二元体系（咪唑盐-水）和三元体系（咪唑盐-脂肪醇-水）中组装出溶致液晶。结果表明，[C10Mim]NO3、[C12Mim]NO3、[C10Mim]CH3COO的水溶液体系中均可以形成六角状溶致液晶，而[C12Mim]CH3COO的水溶液体系中甚至还存在立方相液晶。溶致液晶的形成，不仅跟聚集主体的表面活性有关，更重要的是烷基咪唑盐咪唑环（以2号位H原子为代表）、阴离子、水溶剂分子之间构筑的氢键网络起到了关键作用，加之取代烷基链之间的疏水相互作用，上述因素共同导致了溶致液晶有序结构的建构和稳定。进一步的研究显示，当取代烷基链长较短（n=6、8）时，咪唑盐表面活性不足，无法聚集形成液晶。其它类型的烷基咪唑盐[CnMim]X（X=PF6、OTf、NTf2）因其对水的强烈不溶导致体系分层，形不成溶致液晶。[CnMim]BF4尽管可以在一定程度上溶于水、甚至形成胶束，但阴离子四氟硼酸根构筑氢键网络的能力不足以支持溶致液晶的形成。研究亦表明，脂肪醇的加入，可以实现二元体系六角状溶致液晶的增溶和相态转变，从而出现六角状向层状液晶的转变。含较长链段的脂肪醇甚至可以使含较短链段的[C8Mim]NO3水溶液体系出现溶致液晶相态。此外，1-烷基-3-甲基咪唑盐[CnMim]X（X=BF4、PF6 ; n=2、4、6、8、10）因其结构、作用能力不同，可以进入溶致液晶有序结构的不同区域位置，从而实现对溶致液晶的微观调控。研究还证明，含烷基咪唑盐的新型溶致液晶体系，可以用作模板制备Pt纳米材料。本项目的研究，突破了目前表面活性剂型烷基咪唑盐多为卤化物的限制，而组装的溶致液晶体系，有望在催化、化学反应等方面得到进一步的应用。