The effects of alkylammonium counterions on the aggregation of fluorinated surfactants and surfactant ionic liquids.
The adsorption of ammonium perfluorooctanoate has been investigated at the air-water interface as a function of surfactant concentration at various concentrations of ammonium chloride. The area occupied by the surfactant ion was then calculated from the Gibbs equation with allowance for the presence of salt ions. Independently, the area per surfactant ion at the interface was determined by the technique of neutron reflectiviy. Within experimental error the two sets of measurements were in good agreement.