In situ spectroscopic investigations of adsorbed surfactant and polymer layers in aqueous and non-aqueous systems

Adsorption of surfactants and polymers at the solid—liquid interface is used widely to modify interfacial properties in a variety of industrial processes such as flotation, ceramic processing, flocculation/dispersion, detergency and enhanced oil recovery. A molecular level understanding of the structure of the adsorbed layer is beneficial for improving these processes by manipulating the adsorbed layer. In this paper we discuss the use of fluorescence, electron spin resonance (ESR) and Raman spectroscopy for the study of adsorbed surfactant and polymer layers in aqueous and non-aqueous systems. For example, fluorescence studies using pyrene probe on adsorbed surfactant and polymer layers in aqueous systems along with ESR and Raman spectroscopy reveal the role of surface aggregation and conformation of the adsorbed molecules in controlling the dispersion and wettability properties of the system. In non-aqueous systems, ESR studies using paramagnetic nitroxide probes show how the adsorption of water affects the conformation of adsorbed surfactant molecules and thus affects their dispersion properties.