Study of the Liquid/Vapor Interfacial Properties of Concentrated Polyelectrolyte-Surfactant Mixtures Using Surface Tensiometry and Neutron Reflectometry: Equilibrium, Adsorption Kinetics, and Dilational Rheology

The adsorption of mixtures of poly(diallyldimethylammonium chloride) and sodium N-lauroyl-N-methyltaurate at the water/vapor interface has been studied using drop profile tensiometry and neutron reflectometry. This study sheds light on the mechanisms involved in the adsorption of polyelectrolyte oppositely charged surfactants by the characterization of both equilibrium and dynamic features associated with the layer formation at the fluid interface. The results are discussed in terms of an adsorption equilibration of the interfacial layers as a two-step process, with the initial stages involving the adsorption of polyelectrolyte surfactant complexes formed in the bulk followed by the reorganization of the material at the interface. This work contributes to the understanding of the physicochemical features of systems that undergo complex bulk and interfacial interactions with importance in science and technology.