离子液体在多水相液液平衡体系中的作用

The effect of ionic liquids in aqueous multiphase liquid-liquid equilibrium system

通过用短链离子液体(1-乙基-3-甲基咪唑溴盐[C2mim]Br、1-丁基-3-甲基咪唑溴盐[C4mim]Br)部分或全部取代SDS/DTAB/PEG/NaBr/H2O多水相体系中的无机盐NaBr,用长链离子液体十二烷基-3-甲基咪唑溴盐[C12mim]Br部分取代体系中阳离子表面活性剂DTAB,系统研究了离子液体在分相体系中的作用及其对分相体系性质的影响.研究表明,SDS/DTAB/PEG/NaBr/H2O混合体系形成的四水相体系可以看作"聚合物双水相"与"表面活性剂双水相"共存的结果.短链离子液体([C2mim]Br、[C4mim]Br)较强的亲水性能赋予其较强的盐析能力,在混合体系中表现出明显的盐效应,保证了四水相体系中"聚合物双水相"的存在.短链离子液体与聚合物之间的相互作用及其对表面活性剂之间相互作用的影响均不可忽略.对混合体系的相行为,共存多相的性质有重要的影响.而长链离子液体[C12mim]Br主要通过自身的疏水作用影响"表面活性剂双水相"的性质,充当表面活性剂的角色.然而,[C12mim]Br与DTAB分子结构上的差异,导致表面活性剂分子在"表面活性剂双水相"的两相重新分配,影响了对应两相的体积及萃取能力.可见,通过调节离子液体的烷基链长、混合体系中的含量等可获得具有特定性质的多水相体系.

The effect of ionic liquids on aqueous multi-phase system of DTAB/SDS/PEG/NaBr/H2O has been studied by displacing the inorganic salt NaBr partially or completely with short chain ionic liquids （1-ethyl-3-methyl imidazolebromine [C2mim]Br, 1-butyl-3-methyl imidazole bromine [C4mim]Br） and the cationic surfactant DTAB with long chain ionic liquid （dodecyl-3-methyl imidazole bromine [C12mim]Br）. The results show that the formation of aqueous four-phase system of DTAB/SDS/PEG/NaBr/H2O is the result of the coexistence of ＂polymer ATPS＂ and ＂surfactant ATPS＂. The stonger hydrophilic nature of short chain ionic liquids （[C2mim]Br, [C4mim]Br） endows their stonger salting out ability, which ensured the existence of ＂polymer ATPS＂ in aqueous four-phase system. The interaction between ionic liquids and polymer and the effect of ionic liquids on the interaction among surfactants can not be neglected because all of them have prominent influence on the phase behavior of mixed system and the properties of the coexisted multi-phase. The long chain ionic liquid [C12mim]Br affects the properties of ＂surfactant ATPS＂ by hydrophobic effect and act as the role of surfactant. However, the difference of molecular structure between [C12mim]Br and DTAB leads to the redistribution of surfactant molecules in two phases of ＂surfactant ATPS＂. Correspondingly, the volumes and extraction ability of the two phases are changed. Obviously, aqueous multiphase system with specific properties could be obtained by tailor the alkyl chain length and adjust the content of ionic liquids in mixed systems.