1H NMR探究空间效应对表面活性剂复配体系中协同作用的影响

通过核磁共振氢谱（¹H NMR）实验测量了温度为298.0 K时3种表面活性剂——十六烷基三甲基溴化铵（CTAB）、辛基苯基聚氧乙烯醚（TX-100）和十二烷基硫酸钠（SDS）组成的复配体系CTAB/TX-100、SDS/TX-100和CTAB/TX-100/SDS中各组分的化学位移，得到了各混合体系中CTAB、TX-100和SDS的临界胶束浓度（CMC）.对不同体系中各组分CMC随摩尔分数的变化曲线进行比较，发现了空间效应对表面活性剂复配体系中协同作用的影响在一定的情况下并不逊于静电相互作用：表面活性剂分子的截面积越大，对体系中其他组分的协同作用越强；当组分间存在弱的静电相互作用时，空间效应对协同作用起到更主要的影响.

An NMR Study on How Steric Effects Affect Synergistic Effects in Surfactant Mixtures

NMR spectra of aqueous solutions of cetyltrimethylammonium bromide (CTAB)/triton X-100 (TX-100),sodium dodecyl sulfate (SDS)/TX-100 and CTAB/TX-100/SDS surfactant mixtures were acquired.The proton chemical shifts of each component and their dependence on concentration were determined and used to derive the critical micelle concentrations (CMCs) of CTAB,TX-100 and SDS in each mixture.It was found that,in several cases,the role played by the steric effect in the synergism of surfactant mixtures were not less than that of the electrostatic interaction.The larger the cross sectional area of the polar head was,the greater the synergy would be.It is concluded that the steric effect is a major player in the synergistic effect of surfactant mixtures,especially when the electrostatic interaction is weak.