十二烷基苯磺酸钠气/液界面聚集行为的分子动力学模拟

Molecular dynamics simulation on the aggregation behavior of sodium dodecyl benzene sulfonate at air/water interface

采用分子动力学模拟方法考察了十二烷基苯磺酸钠(SDBS)在气/液界面的聚集行为以及Ca^(2+)和Mg^(2+)对SDBS分子聚集行为的影响。研究结果表明SDBS分子可以在气/液界面形成紧密的单分子层界面膜,并且随着SDBS分子数的增加,界面膜的厚度增加;采用径向分布函数研究了SDBS分子与水分子间的相互作用,结果表明磺酸基和Na^+的静电作用要强于磺酸基和水中氢原子的氢键作用,加入的Ca^(2+)和Mg^(2+)使SDBS分子中磺酸基氧原子和水中氢原子之间的相互作用减弱,说明表面活性剂SDBS抗二价离子能力较差。

The aggregation behavior of sodium dodecyl benzene sulfonate（SDBS） was investigated by molecular dynamics simulation at air/water interface and the effect of calcium ions and magnesium ions on the aggre-gation behavior of SDBS molecules was also discussed.Density profiles were analysized along the z axis for different components.Result showed that SDBS formed a close-packed monolayer at the air/water interface, with the increase of SDBS molecules, the thickness of the interfacial film increased.By comparison with the radial distribution function,it showed that the electrostatic interactions between the sulfonic groups and the sodium ions were stronger than hydrogen bonding interactions between sulfonic groups and hydrogen atoms of the water molecules.This shows that SDBS has weak salt resistance to divalent cations, this may due to the addition of calcium ions and magnesium ions, which make the interaction of the oxygen atoms of sulfonic group and the hydrogen atoms in the water decrease.