Colloidal Dispersions in Non-Aqueous Media - A Fundamental Study of Adsorption and Stabilization Mechanisms

9311940 Somasundaran The stability of colloidal dispersions in non-aqueous media is a phenomenon of vital importance in a number of technologies such as ceramic and tape processing, inks and paints manufacture, oil recovery from tar sands and electrophoretic displays systems. However, major questions on the mechanisms of adsorption of stabilizers on colloidal particles and their stabilization remain largely unanswered. The complex solid- solvent-dispersant interactions that play a critical role in adsorption and subsequent stabilization are not well understood. Also, there is a lack of both fundamental information on the role of water and other polar impurities which have been identified to affect the suspension behavior markedly and on methods to counter the detrimental effects on these impurities. It becomes important to develop such information in order to further advance so many technologies that use processes involving non-aqueous media. Project addresses a multi-pronged approach combining the phenomenological description of suspension stability (settling rate, viscosity), the measurement of physico-chemical properties (adsorption, zeta potential, heats of adsorption) and the use of spectroscopic techniques (ESR, NMR, Fluorescence spectroscopy) to probe micro-structures in solution and at the interface. It focuses on some of the critical issues of adsorption and colloidal stability in non polar media. Specifically, the project investigates the role of the solid surface and the solvent on the adsorption of surfactants on particles from non- aqueous media. Also the role of surface charge and hydration in stabilizing dispersions, the effect of water and other polar impurities on charge development and conformation of the adsorbed molecules investigated. Stabilization effects of macromolecules and surfactant mixtures will be included in the study since they hold maximum practical potential. These studies coupled with the proposed novel spe ctroscopic investigation will enable the PI's to elucidate the fundamental mechanisms of adsorption and stabilization and also to provide guidelines for choosing the appropriate dispersant/solvent combinations and processing schemes to obtain optimum properties for a given non-aqueous dispersion. *** 9311940 Somasundaran The stability of colloidal dispersions in non-aqueous media is a phenomenon of vital importance in a number of technologies such as ceramic and tape processing, inks and paints manufacture, oil recovery from tar sands and electrophoretic displays systems. However, major questions on the mechanisms of adsorption of stabilizers on colloidal particles and their stabilization remain largely unanswered. The complex solid-solvent-dispersant interactions that play a critical role in adsorption and subsequent stabilization are not well understood. Also, there is a lack of both fundamental information on the role of water and other polar impurities which have been identified to affect the suspension behavior markedly and on methods to counter the detrimental effects on these impurities. It becomes important to develop such information in order to further advance so many technologies that use processes involving non-aqueous media. Project addresses a multi-pronged approach combining the phenomenological description of suspension stability (settling rate, viscosity), the measurement of physico-chemical properties (adsorption, zeta potential, heats of adsorption) and the use of spectroscopic techniques (ESR, NMR, Fluorescence spectroscopy) to probe micro-structures in solution and at the interface. It focuses on some of the critical issues of adsorption and colloidal stability in non polar media. Specifically, the project investigates the role of the solid surface and the solvent on the adsorption of surfactants on particles from non-aqueous media. Also the role of surface charge and hydration in stabilizing dispersions, the effect of water and other polar impurities on charge development and conformation of the adsorbed molecules investigated. Stabilization effects of macromolecules and surfactant mixtures will be included in the study since they hold maximum practical potential. These studies coupled with the proposed novel spectroscopic investigation will enable the PI's to elucidate the fundamental mechanisms of adsorption and stabilization and also to provide guidelines for choosing the appropriate dispersant/solvent combinations and processing schemes to obtain optimum properties for a given non-aqueous dispersion. ***