系列烷基芳基磺酸盐的自由能微扰计算

The free energy perturbation calculation of series alkyl aryl sulfonates

采用分子动力学的方法模拟了9种系列烷基芳基磺酸盐在真空和水溶液环境下的结构与相互作用。利用自由能微扰方法计算了9种结构的水合自由能,结果表明:随着芳环向长烷基链的中间位置移动,胶束化能力下降,随着芳环上长烷基链碳数的增加、随着芳环上短烷基链个数的增加和短烷基链碳数的增加,胶束化能力提升;通过对自由能的力的分解和原子对的径向分布函数分析,揭示了胶束的驱动力是疏水效应综合作用的结果;根据氢键的图形定义,分析了系列表面活性剂极性头与周围水分子的氢键相互作用,发现氢键的数目能增强或者减弱分子脱离胶束体的趋势,进而影响胶束的稳定性;同时计算了水分子中氢键的生存周期。

The interaction of nine alkyl aryl sulfonates in the vacuum and solution was simulated used by a molecular dynamics method. The solvation free encrgy which have nine structure was calculated from free energy perturbation （FEP）, and the result indicate： as the aromatic ring shift from the edge to the middle of the long alkyl chain, the formation ability of mieelle and the micelle stability is decreased. With the aromatic ring carbon number increasing of the long alkyl chain and with the number of aromatic ring of the short alkyl chain the micelle slability is increasing, it so as to the aromatic ring carbon number increasing of the short alkyl chain. Through disassembling tree energy and analyzing radial function of the twain atom, the result of hydrophobic effect synthesis effect was micelle driving force. The reciprocity of scries polarity of surfactant and the hydrogen bond of water was analyzed, which based on the graph definition of the hydrogen bond. We found that the number of hydrogen bond could strengthen or weaken the current of molecule deviating micelle, and then effected the stability of micelle. At the same time, the existent cycle of hydrogen bond in water molecule could be calculated.