Aggregation behavior of ionic liquids in aqueous solution studied by physical methods



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The role of ILs as a surface active agents needs to be fully understood. Based on the previous work, we characterized the micellization of 1-alkyl-3-methyl-limidazolium bromide ([Cnmim][Br], for n = 8, 10, 12, 14, 16), and 1,3-dialkyl imidazolium bromide ([(Cn)2im][Br], for n = 8, 10, using pyrene fluorescence, surface tension, and conductivity measurements; the aggregation numbers of micelles in water were also obtained using the fluorescence quenching technique. The contact angle of the IL solution on the silicon wafer was measured and analyzed. The data obtained gave a more comprehensive understanding about the micelle formation process of these ILs. Information about the micro-polarity in the micelle interior region, packing density of the ILs in the micelle phase, growth of the micelle with the concentration, absorbance of ILs at the interface, etc. were obtained. The symmetry effect on the aggregation behavior of the two structurally related IL groups was studied. The symmetric ILs behave very differently from the asymmetric ILs due to their distinct structure.



Imidazolium based ionic liquid, Micelle, Conductivity, Aggregation number, Fluorescence, Surface tension, Contact angle