利用电导法研究了298．15 K时十四烷基二甲基苄基氯化铵( TDBAC)与咪唑型离子液体表面活性剂Cn mimBr(n=12,16)混合胶束性质,考察了极性溶剂N,N-二甲基甲酰胺(DMF)对TDBAC/C16mimBr混合体系胶束化的影响。结果表明,混合体系在水溶液和DMF水溶液中都存在协同效应。随DMF体积分数的增加,TD-BAC/C16 mimBr混合体系临界胶束浓度( cmc)增大,而反离子结合度减小。利用胶束理论模型计算了混合胶束的组成、相互作用参数和活度系数,以及胶束形成混合自由能、混合熵和超额自由能等热力学函数。随DMF体积分数增加,协同作用下降,胶束形成的自发性降低。水溶液中混合胶束形成是焓效应与熵效应共同作用的结果,而在20%DMF水溶液中,胶束形成是熵驱动。%The micellization behaviors of binary mixtures of tetradecyldimethylbenzylammonium chloride( TDBAC) and imidazole i-onic liquids CnmimBr(n=12,16)were investigated in N,N-dimethylformamide(DMF)+water mixed solvent at 298. 15K using elec-trical conductivity measurement. It is shown there are synergistic effects on mixed micelle formation both in water and DMF+water mixed solvent. And the synergistic effect in TDBAC/C12 mimBr mixture is greater than one in TDBAC/C16 mimBr mixture. The mixed micelle is rich in surfactant which has high surface activity. With the increase of DMF in mixed solvent,the critical micelle concen-tration(cmc)of TDBAC/C16mimBr mixture increases,while the degree of counter ion binding(g)decreases. The composition of mixed micelles and the interaction parameters were evaluated from the cmc of single and mixed systems using Rubingh’ s and Mo-tomura’s theories. Activity coefficients of mixed systems reflect the extent of non-ideality. For the mixture of TDBAC(1)/C16mimBr (2),the Gibbs free energy of micelle formation is negative within the whole range of the mole fraction of TDBAC. Both in water and DMF+water mixed solvent,the minimum of the ΔGm,exc appears at the same composition of bulk solution namely:α1≈0. 7. It indi-cates that mixed micelle is easiest formed at this composition. The interaction parameters become progressively more positive with increasing content of DMF in mixed solvent. Consequently,the interaction between two cationic surfactants changes into weak. The excess Gibbs free energy demonstrates that the spontaneity of micelle formation is reduced with the addition of DMF. The effect of entropy and enthalpy on micellization is the same importance in water. Whereas the micelle formation is found to be almost entropy-driven in 20%( V/V) DMF aqueous solution.
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