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利用等温滴定微量量热法和电导法研究了具有不同疏水链长并且疏水链尾部含有对硝基苯醚基团的Gemini表面活性剂胶束化过程的热力学,分别利用相分离模型和质量作用模型对观察焓与浓度的关系曲线进行拟合,获得了胶束化过程的热力学参数.两种模型获得的胶束化焓一致,均为较大负值,而吉布斯自由能却相差较大.用相分离模型得到的胶束化过程的热容变化均为负值,并随链长增加绝对值增大,胶束化过程总的热容变化主要来自非极性的烷基链去水合产生的热容变化,证明处于疏水链末端的对硝基苯醚基团在表面活性剂形成胶束后依然与水相接触.质量作用模型获得的胶束聚集数随疏水链长增加逐渐下降,这是由具有长疏水链的表面活性剂形成预胶束所导致.
The thermodynamics of Gemini surfactant micelles with different hydrophobic chain lengths and hydrophobic groups in the tail of hydrophobic chains were studied by isothermal titration microcalorimetry and conductivity method. The phase separation model and the mass effect model The thermodynamic parameters of the micellization process were obtained by fitting the curves of the observed enthalpies with the concentration.The enthalpy of micelles obtained by the two models were all in agreement with each other and the Gibbs free energies were quite different The change of heat capacity of the micellization process obtained by the phase separation model is negative and increases with the increase of the absolute value of the chain length. The change of the total heat capacity of the micellization mainly comes from the non-polar alkyl chain dehydration The change of heat capacity showed that the para-nitrophenylether group at the end of the hydrophobic chain was still in contact with water after the surfactant formed micelles.The mass concentration of micelles obtained by the mass effect model decreased gradually with the increase of hydrophobic chain length, This is caused by the formation of premicelles with surfactants with long hydrophobic chains.