Fluoride ion binding and adsorption affinity of polyelectrolytes

Poly (2,6-dimethyl-1,4-phenylene oxide) substituted with quaternary fluoride salts and phosphorous-containing pendent groups were prepared as pH 7 polyelectrolyte solutions. The ability of these polyelectrolytes to bind fluoride ions in solution and to adsorb onto calcium phosphate (hydroxyapatite) surfaces was studied as a function of the number and type of substituent groups. Fluoride binding was found to be enhanced by cross-linking, which maintains the polyelectrolyte in a compressed-coil conformation. Adsorption affinity and resistance to desorption were increased by the presence of phosphorous-containing groups, especially phosphonate esters. These factors will be important in designing polyelectrolytes to remove counter-ions from solution and concentrate them at surfaces for biomedical and industrial applications.