离子液体在多水相液液平衡体系中的作用
摘要
The effect of ionic liquids on aqueous multi-phase system of DTAB/SDS/PEG/NaBr/H<sub>2</sub>O has been studied by displacing the inorganic salt NaBr partially or completely with short chain ionic liquids (1-ethyl-3-methyl imidazolebromine [C<sub>2</sub>mim]Br, 1-butyl-3-methyl imidazole bromine [C<sub>4</sub>mim]Br) and the cationic surfactant DTAB with long chain ionic liquid (dodecyl-3-methyl imidazole bromine [C<sub>12</sub>mim]Br). The results show that the formation of aqueous four-phase system of DTAB/SDS/PEG/NaBr/H<sub>2</sub>O is the result of the coexistence of "polymer ATPS" and "surfactant ATPS". The stonger hydrophilic nature of short chain ionic liquids ([C<sub>2</sub>mim]Br, [C<sub>4</sub>mim]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 [C<sub>12</sub>mim]Br affects the properties of "surfactant ATPS" by hydrophobic effect and act as the role of surfactant. However, the difference of molecular structure between [C<sub>12</sub>mim]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.