Synthesis And Critical Micelle Concentration Determination Of Four Kinds Of Dodecyl Imidazole And Pyridine Ionic Liquids

Ionic liquid surfactant is a kind of new type entirely composed of ion surface active material,in this paper,the 1-dodecyl-3-methyl imidazole bromine salt,1-dodecyl-3-methyl imidazole four fluorine boric acid salt,N-dodecyl bromide pyridine,four fluoboric acid,N-dodecyl pyridine four kinds of ionic liquids for synthesis,characterization and surface performance testing.In this experiment,four ionic liquids were synthesized by two-step synthesis method,and the structures of the samples were characterized by ~1H-NMR,¹³C-NMR and ¹⁹F-NMR.The critical micelle concentrations（CMC）of four surfactants were measured by conductivity and surface tension methods.The results showed that the critical micelle concentrations were determined by electrostatic effect and hydrophobic effect.When the anion is BF4^-,the ionic liquid has a lower CMC,and BF4^-has a better hydrophobic effect,which makes the ionic liquid easier to form micelles.The free energies of micelle formationΔG_m^θof the four kinds of ionic liquids were calculated.TheΔG_m^θof the four kinds of ionic liquids were all less than zero,indicating that the micelle formation was spontaneous.The results show that BF4^-has better surface performance than Br^-,that is,the ionic liquid of tetrafluoroborate has higher adsorption efficiency at the same temperature,and its aqueous solution has lower surface tension,so it is a more ideal surfactant.The surface activity of imidazole and pyridine ionic liquids with the same anion and carbon chain length was compared with that of pyridine ionic liquids.The surface activity of imidazole and pyridine ionic liquids with the same anion and carbon chain length was compared with that of pyridine ionic liquids.The surface activity of imidazole and pyridine ionic liquids with the same anion chain length was compared with that of pyridine ionic liquids with the same anion chain length.At the same time,imidazolium ionic liquid surfactants have a wider range of applications and more types.Therefore,among the four types of ionic liquids discussed in this paper,1-dodecyl-3-methylimidazolium tetrafluoroborate is the ideal surfactant.