Role of Counterion in the Adsorption of Ionic Amphiphiles at Fluid Interfaces.

This communication represents the chemical alternative to the previous two papers dealing with the influence of positively charged alkali cations on the adsorption properties of the series of the standard surfactant system of alkali-perfluorocarbon octanoates. Now, this contribution describes the adsorption properties of the negatively charged cationic surfactant series of trimethyldodecyl-ammonium halides. In our latest contributions, we have put forward a new model of adsorption of ionic surfactants.

Adsorption properties of surface chemically pure sodium perfluoro-n-alkanoates at the air/water interface: counterion effects within homologous series of 1:1 ionic surfactants.

The unusual behavior of saturation adsorption calculated from experimental equilibrium surface tension (σ(e)) versus logarithm of concentration (c) isotherms within the homologous series of aqueous sodium perfluoro-n-alkanoate solutions represents a particular problem in the adsorption of homologous ionic 1:1 amphiphiles at fluid interfaces. Special precautions were taken to guarantee surface-chemical purity for all solutions, avoiding falsifying effects by surface-active trace impurities. Surprisingly, all homologues' adsorption isotherms reveal ideal surface behavior.