通过酸碱中和反应制备了阴/阳离子表面活性剂十四烷基三甲基月桂酸铵, 发现其对石蜡油/水体系具有很强的乳化能力, 通过简单振荡便能形成均一、稳定的乳液. 光学显微镜观察发现乳液液滴的直径从几微米到几百微米不等, 形成密堆积结构. 增大表面活性剂含量使液滴的平均尺寸和多分散度降低. 流变学研究表明, 乳液具有明显的剪切稀释行为, 在同一水体积百分含量下, 随表面活性剂含量的增加, 乳液粘度增大, 且表现出一定的屈服应力. 振荡剪切结果表明乳液具有明显的粘弹性, 在整个频率测量范围内, 弹性模量均高于粘性模量. 此外, 我们还考察了水体积百分含量对乳液性能的影响.

Salt-free cationic/anionic surfactant mixtures (catanionics) have received considerable attention in recent years due to their high surface activity and rich phase behavior. Although there have been extensive reports about their aggregation behavior, rheological properties and interaction with guest molecules in aqueous solutions, investigations in nonaqueous solutions and/or in solvent mixtures are rare. Typically, emulsions have enormous applications both in industry and daily life, and catanionics have long been predicted to be good emulsifiers. However, study in this direction is still in its infancy. Here, by acid-base neutralization we have prepared a catanionic surfactant, tetradecyltrimethyl ammonium laurate (TTAL), which was found to be able to effectively emulsify paraffin oil/water system. The emulsions can be obtained by simple hand-shaking, which is in sharp contrast to many of existing emulsions which can be only obtained through high-energy input. Optical microscopy observations revealed the presence of polydisperse, closely-packed emulsion droplets with diameters ranging from several micrometers to hundreds of micrometers. An increase in the amount of added TTAL at fixed water content induces a decrease of both the averaged size and polydispersity of the droplets. In contrast, the influence of the water content on the averaged size and polydispersity of the droplets is not obvious. Steady-state shear measurements indicated that the emulsions are shear-thinning, presumably due to the destruction of the close-packing of the emulsion droplets under shear. Oscillatory shear measurements revealed that the emulsions are viscoelastic with the elastic modulus higher than the viscous modulus over the whole investigated frequency range. At higher amount of added TTAL, the viscoelasticity of the emulsion also becomes higher and the emulsion begins to exhibit a yield stress. These observations are reminiscent of the characteristics of closely-packed vesicles formed by catanionics in water, and indicate that this unique class of surfactant can be potentially utilized for the construction of new generation of emulsions.