The effect of binary solvents on adsorption of poly(vinylpyrrolidone) on titanium dioxide and graphite particles

The effect of binary solvents on adsorption of poly(vinylpyrrolidone) on titanium dioxide and graphite has been studied by measuring adsorbed amount, dispersion stability, and ESR spectra at the solid/liquid interface, In water/ethanol and ethanol/hexane binary solvents, the adsorption of PVP on titanium dioxide is appreciably enhanced by an increase of ethanol ratio in the water/ethanol binary solvents, but is slightly increased by an increase of hexane ratio in the ethanol/hexane binary solvents, On the other hand, the adsorption of PVP on graphite shows a maximum from ethanol for both water/ethanol and ethanol/hexane binary solvents, This PVP adsorption is significantly affected with a competitive adsorption of the solvent molecules, The dispersion stability of titanium dioxide by the adsorption of PVP is high in a wide PVP concentration range, irrespective of the kinds of binary solvents, whereas that of graphite is dependent on the PVP concentration, These differences in the dispersion stability are correlated with the fraction of bound segments of PVP adsorbed which has been estimated by means of ESR using a spin-labeled PVP. (C) 1996 Academic Press, Inc.