The surface properties and micellization behavior of binary mixture of ionic liquid surfactant 1-hexadecyl-3-methylimidazolium bromide (C₁₆mimBr) and nonionic surfactant Triton X-100 (TX100) were investigated in water and in 20% (V/V) ethylene glycol (EG) aqueous solution, respectively, employing tensiometric technique. It is shown there are synergistic effects on mixed adsorbed film and mixed micelle formation both in water and in 20% ethylene glycol aqueous solution. When the molar fraction of TX100 in mixture is about 0.65, the synergistic effect is at its optimum. The critical micelle concentration (cmc) of the mixture increases with EG being added in solvent. The established theories of Rubingh and Motomura were applied to determine the molar fraction of the different components, the interaction parameters and several thermodynamic properties of the mixed adsorbed film and micelle phase. It was found that the compositions of mixed monolayer and micelle, and the excess free energy of micelle formation from Rubinghs model and Motomuras model were in agreement.

Key words: ionic liquid surfactant, mixed polar solvent, surface property, micellization behavior, regular solution theory