Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (1): 83-89.doi: 10.3866/PKU.WHXB201411191


Counterion Effects on the Properties of Sulfate Surfactants at the Air/Liquid Interface by Molecular Dynamics Simulation

HU Song-Qing1, JI Xian-Jing1, FAN Zhong-Yu2, ZHANG Tian-Tian1, SUN Shuang-Qing1   

  1. 1. College of Science, China University of Petroleum(East China), Qingdao 266580, Shandong Province, P. R. China;
    2. Exploration and Development Research Institute, Huabei Oilfield Company, Renqiu 062552, Hebei Province, P. R. China
  • Received:2014-10-14 Revised:2014-11-19 Published:2014-12-25
  • Contact: HU Song-Qing
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51201183), Promotive Research Fund for Excellent Young and Middle-Aged Scientists of Shandong Province, China (BS2013CL033), and CNPC Innovation Foundation, China (2011D-5006-0202).


Molecular dynamics (MD) simulations have been carried out to study the micro-interfaces between counterions (Li+, Na+, K+, Rb+, Cs+) and dodecyl sulfate surfactant at the air/liquid interface. The morphology of the monolayer was analyzed by the density profile of the surfactant components, and the interactions between the polar head groups of the surfactants and the counterions were analyzed using the radial distribution function (RDF). The results showed that the interfacial thickness and thicknesses of the Stern and diffusion layers increased as the radius of counterion increased, whereas the surface tension and the degree of counterion association at the adsorbed layer decreased as the radius increased. These results indicated that the different counterions had a significant effect on the adsorption behavior of the dodecyl sulfate surfactants at the interface.

Key words: Dodecyl sulfate, Counterion, Air/liquid interface, Electrical double layer, Molecular dynamics