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采用分子动力学方法研究了两性表面活性剂十二烷基二甲基磺丙基甜菜碱在气-液界面的聚集结构,分析了影响液膜稳定性的因素。结果表明,界面生成能对界面膜的稳定有重要作用,增加表面活性剂在液膜上的浓度利于界面膜的稳定。通过表面活性剂头基与水分子之间的径向分布函数,可把表面活性剂周围的水分子分为3种类型:结合水、捕获水和自由水。其中表面活性剂通过氢键、静电作用等束缚结合水和捕获水的能力与液膜稳定性密切相关,模拟发现磺基甜菜碱对水分子具有强烈的结合作用,是泡沫稳定的重要影响因素。
The molecular structure of the amphoteric surfactant, dodecyl dimethyl sulfopropyl betaine, at the gas-liquid interface was studied by molecular dynamics method. The factors that affect the stability of the liquid film were analyzed. The results show that the interfacial formation can play an important role in stabilizing the interfacial film and increasing the concentration of the surfactant on the interfacial film. By means of the radial distribution function between the surfactant head group and water molecules, the water molecules surrounding the surfactant can be divided into three types: bound water, trapped water and free water. Among them, the ability of surfactants to bind and capture water by binding hydrogen bonds and electrostatic interactions is closely related to the stability of the liquid film. The simulation shows that sulfobetaine has a strong binding effect on water molecules and is an important factor for foam stability.