中文摘要：

用密度泛函理论,在B3LYP/6-31G水平上,对十二烷基磺酸盐和羧酸盐阴离子表面活性剂与阳离子（Na^＋,Ca^2＋,Mg^2＋）形成的离子对进行结构优化,从分子水平上研究表面活性剂与阳离子之间的相互作用.计算结果表明：磺酸盐和羧酸盐表面活性剂均采用2∶1型,即极性头中两个氧原子与阳离子发生稳定结合;在与阳离子结合之前,表面活性剂分子上的α-亚甲基带有明显的负电荷,因此将其归为极性头;但在阳离子电荷诱导下,α-亚甲基转而带有部分弱正电荷,使极性头范围缩小.计算也发现,表面活性剂尾链带有弱正电荷,使胶束内核带有了部分极性,利于表面活性剂在溶液中的聚集,此种极性介于烷烃油相和水相的极性之间.

英文摘要：

The ion-pairs of the anionic surfactants （dodecyl sulfonate, dodecyl carboxylate） and the cations （Na＋, Ca2＋, Mg2＋） were optimized using density functional theory （DFT） at the B3LY/6-31G level and the interaction between the surfactants and ions were studied at the molecular level.The results showed that：i） a 2∶1 type of ion-pair was formed in which two oxygen atoms from the polar group in the surfactant bound with one ion; ii） the α-methylene nearest the headgroup should be classified as the part of the polar head because of its negative charge before ion bonding; iii） the charge of the α-methylene group can be converted from a weak negative into a weak positive charge by the cations, which decreased the effect of the polar headgroup.This calculation also showed that the tail chain had a weak positive charge in the micelle resulting in the core of the micelle having polarity.This core polarity of the micelle is somewhere between the oil phase polarity and the water phase polarity, which favors surfactant aggregation in solution.