Properties of mixed surfactants containing ionic liquid surfactant are investigated in this paper. The other surfactants mixed with C12mimBr are several common surfactants, including Gemini 12-3-12, DTAB and SDS. Both of Rubingh-Margules model and Rubingh-regular solution model are used to calculate the critical micelle concentration and the composition of mixed micelle. It is observed that molecular structure and interaction between the charged head groups have great effects on the properties of mixed surfactants. The mixed behavior of C12mimBr and Gemini 12-3-12 with great difference in the molecular structure is non-ideal, while it is almost ideal for mixture of C12mimBr and DTAB with the same hydrophobic chain length and different hydrophilic head group only. Due to the strong attractive interaction between the opposite charged head groups, of course the mixed behavior of C12mimBr and SDS is absolutely non-ideal. Moreover, results of the micelle composition from the two models are almost the same; however, the prediction result of the critical micelle concentration is obviously better from Rubingh-Margules model than from Rubingh-regular solution model.

Key words: ionic liquid surfactant, common surfactant, mixing behavior, critical micelle concentration, micelle composition