C12-s-C12·2Br与低碳醇混合水溶液胶团化行为的温度效应和焓/熵补偿

季铵盐Gemini表面活性剂C12-s-C12·2Br(s=2,3,4,6)与丙醇、丁醇、戊醇、己醇混合水溶液的In(cmc)随温度升高而逐渐增大.计算所得热力学数据表明,C12-s-C12·2Br与醇混合胶团化过程服从熵驱动机理,也出现了焓/熵补偿现象.随着温度上升,熵驱动力增大,在指定温度时,醇分子烷烃链上碳原子数n增大使△Gm0值减小,胶团结构更加稳定;而增加s使值增大,胶团稳定性下降.

Temperature Effect and Enthalpy-entropy Compensation of the Mixed Micellization of C12-s-C12·2Br and Alcohol in Aqueous Solution

The mixed micellization of quaternary ammonium gemini surfactants C12-s-Ci2 2Br (s=2,3, 4,6) and alcohols(n-propanol, n-butanol, H-pentanol and n-hexanol) in aqueous solutions has been investigated at different temperatures by using conductivity measurements. The results show that the critical micelle concentrationdn(cmc)) gradually increases with increasing temperature. The thermodynamic parameters calculated by phase separation model indicate that the mixed micellization of C12-s-C12 2Br and alcohol is an entropy-driven process. The entropy-driven is enhanced as temperature is going up. All plots of enthalpy-entropy compensation exhibit an excellent linearity. At a fixed temperature, G is decreased and the micelle stability is enhanced with increasing the carbon atom number(n) in the alkyl chain of alcohol molecule. However, these properties have an opposite trend with increasing s.