| Abstract
| - Aqueous solutions of three kinds of surface active ionic liquids composed of the 1-alkyl-3-methylimidazoliumcation have been investigated by means of surface tension and electrical conductivity measurements at room temperature(298 K). The surface tension measurements provided a series of parameters, including critical micelle concentration(cmc), surface tension at the cmc (γcmc), adsorption efficiency (pC20), and effectiveness of surface tension reduction(Πcmc). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γmax)and minimum surface area/molecule (Amin) at the air−water interface were estimated. The effect of sodium halides,NaCl, NaBr, and NaI, on the surface activity was also investigated. It was found that both the pC20 and the Πcmc wererather larger than those reported for traditional ionic surfactants and the cmc values were somewhat lower than thosefor typical cationic surfactants, alkyltrimethylammonium bromides, and comparable to typical anionic surfactants,sodium alkyl sulfates. These results demonstrate that the surface activity of long-chained imidazolium IL is somewhatsuperior to that of conventional ionic surfactants.
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