Acta Phys. -Chim. Sin. ›› 2006, Vol. 22 ›› Issue (12): 1451-1455.doi: 10.1016/S1872-1508(06)60074-0

• ARTICLE • Previous Articles     Next Articles

Interfacial Tension of the Aqueous Two-phase Systems of Cationic-Anionic Surfactant Mixtures

RUAN Ke;ZHANG Ling;TANG Jiao-Ning;XIAO Jin-Xin   

  1. (Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China; Shenzhen Key Laboratory of Special Functional Materials, Shenzhen University, Shenzhen 518060, P. R. China)
  • Received:2006-05-05 Revised:2006-06-28 Published:2006-12-06
  • Contact: XIAO Jin-Xin

Abstract: Interfacial tensions of the aqueous two-phase systems formed by cationic-anionic surfactant mixtures were measured using spinning drop method. The effects of surfactant structure, molar ratio of cationic surfactants to anionic surfactants, surfactant concentration, salt, and temperature on the interfacial tensions were investigated. It was shown that the values of the interfacial tensions of the aqueous two-phase were in the scale of ultra-low interfacial tensions at certain molar ratios of cationic to anionic surfactants. Three types of interfacial tension curves were observed. The first curve comprised two curves that were located on either side of 1:1 molar ratio, and the interfacial tension decreased with the increase of excessed surfactant component. The second one was a saddle-shaped curve that strode over the 1:1 molar ratio. The third type was a saddle-shaped curve that was located beside the 1:1 molar ratio. The types of interfacial tension depended on the molecular structure of the surfactants such as the hydrophilic groups and the lengths and symmetry of hydrophobic chains.

Key words: Cationic-anionic surfactant, Aqueous two-phase system, Interfacial tension