Adsorption of Oppositely Charged Polyelectrolyte/Surfactant Complexes at the Air/Water Interface:Formation of Interfacial Gels

摘要

The adsorption and complexation of polystyrene sulfonate(a highly charged anionic polyelectrolyte)and dodecyltrimethylammonium bromide (a cationic surfactant)at the air-water interface can lead to interfacial gels that strongly influence foam-film drainage and stability.The formation and characteristics of these gels have been studied by combining surface tension,ellipsometry,and foam-film drainage experiments.Simultaneously the solution electromotive force is measured and used to track the polymer-surfactant interactions in the bulk solution.We find that surface gelation occurs above the critical aggregation concentration in solution but before bulk precipitation of the polymer-surfactant complexes.Furthermore,we reveal that strong readsorption of polymer-surfactant complexes occurs during the resolubilization of the precipitated complexes at high surfactant concentrations(i.e.,critical micelle cencentration).Seemingly overlooked in the past,this readsorption significantly influences the surface rheological Properties and foam-film drainage of these systems.