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Indexed by:期刊论文

Date of Publication:2008-03-01

Journal:JOURNAL OF SURFACTANTS AND DETERGENTS

Included Journals:SCIE、EI

Volume:11

Issue:1

Page Number:73-78

ISSN No.:1097-3958

Key Words:unsymmetrical bolaform surfactant; ionic strength; surface tension

Abstract:By performing measurements of the equilibrium surface tensions of electrolyte solutions of three unsymmetrical bolaamphiphiles, each of which has an aromatic ring and a omega-carboxyalkyl chain in its molecular structure, we conclude that the carboxyl and sulfonate groups at both ends of the molecule-which enter the solution while the hydrophobic chain extends into the air-can force these surfactants to adopt a looped configuration which looks like the letter "U" upside-down, resulting in regular arrangements at the air/water interface and micelles in bulk solution. Surface tension measurements of these surfactants as a function of added salt reveal the limiting surface tension to be less sensitive to the ionic strength in LiCl solution and significantly sensitive to divalent Ca2+ and Mg2+ ions in hard water. This result reveals that the looped configuration of the molecule is the dominant factor in determining whether the molecules of this surfactant are sensitive to ionic strength or not. This paper also reports briefly on the effect of the interactions of divalent Ca2+ and Mg2+ ions with unsymmetrical bolaamphiphiles on the turbidity of hard water. These results suggest that the interactions of divalent Ca2+ and Mg2+ ions with carboxyl groups are strong, and the two breaks in the surface tension curves disappear. In 200 ppm hard water, the turbidity appears over just a small range of surfactant concentrations, showing that the presence of the Ca2+ and Mg2+ ions has little effect on the application of these surfactants.