Acta Phys. -Chim. Sin. ›› 1996, Vol. 12 ›› Issue (11): 976-980.doi: 10.3866/PKU.WHXB19961104

• ARTICLE • Previous Articles     Next Articles

Effect of Organic Ammonium Salts on the Surface Activity and Solubility of Fluorocarbon Surfactant

He Shao-Guang,Zhao Guo-Xi   

  1. Institute of Physical Chemistry,Peking University,Beijing 100871
  • Received:1996-05-29 Revised:1996-07-08 Published:1996-11-15
  • Contact: Zhao Guo-Xi


The surface tension of the aqueous solutions of organic ammonium salts and potasium 3-oxa-perfluorononane-sulfonate (FC-53)has been determined. The effect of organic ammonium salts on the surface activity and solubility of FC-53 has been investigated. It is found that the non-surface active ammonium salts ((CH3)3NHCl, ((C2H5)3NHCl,(HOC2H4)3NHCl,and (C2H5)4NBr) and the surface active ones (n-C4H9)4NBr and n-C8H17N(CH3)3Br) all can enhance the surface activity of FC-53, and the former can make FC-53 more water-soluble whereas the latter can not. The Gibbs adsorption equations for these mixed systems have been derived and the molecular interactions and compositions in the surface layers, especially for the systems containing surface active organic ammonium salts, have been obtained. It is concluded that, owing to the strong attraction (in addition to the hydrophobic interaction) between the two oppositely charged surface active ions, the mixtures with surface active organic ammonium salts are very surface active and the surfactant hydrophobic chains are close-packed with the orientation toward air, and for (n-C4H9)4N+ group, the n-butyl chain is not stretched but has a bending conformation. 

Key words: Perfluoroalkanesulfonate, Surface activity, Solubility, Structure of surface layer, Surface molecular interactions