Electron Spin Resonance Spectrometer to Probe Microstructures at Interfaces

The purchase of an Electron Spin Resonance Spectrometer is requested. The system will consist of a basic console, an analog recorder and display, appropriate microprocessor systems for the superheterodyne and field controller and data handling systems. It will be used to develop a full understanding of the process of adsorption of various surfactants an polymers and the effect of different parameters on the structure of the adsorbed layers. Adsorption of surfactants and polymers at the solid/liquid interface modify the surface properties of the solid. Such modifications are used in many industrial processes such as flocculation, enhanced oil recovery and flotation. In addition, the adsorbed layers, particularly self-assemblies such as hemimicelles have potential use in novel applications such as catalysis and isotope separation. Hence, understanding of the adsorption phenomena is of great importance. Earlier work focussed on understanding the physico-chemical mechanisms of adsorption of surfactants and polymers by measuring adsorption density, zeta potential, wettability and adsorption enthalpies. Such studies have helped in generating a mechanistic picture of the structure of the adsorbed layer. However, it has become clear that a molecular level understanding of adsorption is essential for the full utilization of it in various processes. Recently, EST has been used probe absorbed layers on solids on a molecular level. These studies have demonstrated the potential of ESR Spectroscopy to elucidate the mechanisms of formation of adsorbed layers and hence of adsorption. ESR spectroscopy is also the technique which recently proved very useful for us in examining the orientation of surfactants on solids in non-aqueous medium. Future research plans using the equipment will includes conformational changes of polymers with flocculation and dispersion of fines. Polymers labelled with nitroxide type probes will be used for such studies. Another important area of investigation is to elucidate the role of surfactant