IN-SITU SPECTROSCOPIC INVESTIGATIONS OF ADSORBED SURFACTANT AND POLYMER LAYERS IN AQUEOUS AND NONAQUEOUS SYSTEMS

Adsorption of surfactants and polymers at the solid-liquid interface i s used widely to modify interfacial properties in a variety of industr ial processes such as flotation, ceramic processing, flocculation/disp ersion, detergency and enhanced oil recovery. A molecular level unders tanding of the structure of the adsorbed layer is beneficial for impro ving 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 l ayers in aqueous and non-aqueous systems. For example, fluorescence st udies 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 c ontrolling the dispersion and wettability properties of the system. In nonaqueous systems, ESR studies using paramagnetic nitroxide probes s how how the adsorption of water affects the conformation of adsorbed s urfactant molecules and thus affects their dispersion properties.