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本文通过等温滴定量热法(ITC)、电导法和浊度法研究了阴离子生物表面活性剂脱氧胆酸钠(NaDC)及其与相反电荷的十二烷基三甲基溴化铵(DTAB)在水溶液中的自组装热力学.ITC结果支持了NaDC在水溶液中先生成预胶束再形成稳定胶束的分步聚集模型,由此得到了NaDC的预胶束和胶束化过程的一系列热力学参数,并讨论了它们形成的热力学机理.进一步研究了具有头-尾链式和疏水-亲水刚性面式非对称结构的DTAB/NaDC混合体系的聚集热力学行为,得到了富NaDC临界混合胶束浓度(cmcmix)、富DTAB临界胶束浓度(CM)及对应过程的转变焓.结果表明,NaDC面式结构与DTAB链式结构的对称性差异以及相反电荷的相互作用,导致混合体系有别于单一表面活性剂或头-尾链式结构的混合体系的聚集行为.混合溶液的聚集行为受控于表面活性剂浓度和摩尔分数的变化.富NaDC胶束化过程为熵驱动,而富DTAB的两种胶束形态转变过程为熵焓共同驱动的热力学机理.这些结果对于从热力学角度认识胆汁酸盐的自组装机理以及与传统的头-尾链式结构的表面活性剂相互作用机理和相行为有重要的意义.
In this paper, the anionic biosurfactant sodium deoxycholate (NaDC) and its oppositely charged dodecyltrimethylammonium bromide (DTAB) were studied by isothermal titration calorimetry (ITC), conductivity and turbidity methods. The self-assembly thermodynamics in aqueous solution.The results of ITC support the step-by-step aggregation model of NaDC in micellar solution and the formation of stable micelles, and obtained a series of thermodynamics The thermodynamics mechanism of their formation is also discussed.The aggregation thermodynamics of DTAB / NaDC mixed system with head-tail chain and hydrophobic-hydrophilic rigid surface asymmetric structure is further studied, and the NaDC-rich mixed micelles (Cmcmix), the critical micelle concentration (CM) of DTAB, and the enthalpy of formation of the corresponding process.The results show that the symmetry difference between NaDC surface structure and DTAB chain structure and the opposite charge interaction lead to the difference between the mixed system Single surfactant or head-tail chain structure.The aggregation behavior of the mixed solution was controlled by the change of surfactant concentration and molar fraction.NF-rich micellization process was entropy-driven and DT-rich The two micellar morphological transitions of AB are the thermodynamic mechanisms driven by the enthalpy of enthalpy.These results are useful for understanding the self-assembly mechanism of bile salts and the interaction with the traditional head-tail chain structure surfactant and Phase behavior has important implications.