气液界面上磺基甜菜碱两性表面活性剂分子动力学模拟

Molecular dynamics simulation of zwitterionic surfactant sulfobetaine at the vapor/liquid interface

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 aggregation morphology of zwitterionic surfactant dodecyl hydroxy-propyl sulfobetaine at the vapor-liquid interface was investigated using molecular dynamics method,and the effect of film stability was discussed.Depending on the interface formation energy,the increasing number of surfactant molecules at the interface helped the stability of liquid membrane.Through the radial distribution functions between the head groups of surfactant and water molecules, the water molecules around surfactant molecules were divided into three types,bound water,trapped water and free wa-ter.There were important relationships between the stability of foam and the ability of surfactant binding with water molecules through hydrogen bonding and electrostatic interaction.The results showed that this zwitterionic surfactant had strong binding effect to water molecules in the stability of foam.