Adsorption mechanism(s) of poly(ethylene oxide) on oxide surfaces

Adsorption of poly(ethylene oxide) (PEG) on various oxides and the flocculation behavior of PEG-coated particles was investigated to elucidate the polymer adsorption mechanism(s). It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen of PEG, a Lewis base, to induce adsorption and subsequent flocculation of the substrate particles. In general highly acidic oxides of the type MO3, M2O5,, and MO2 are expected to adsorb and flocculate with PEG. Accordingly, MoO3, V2O5, and SiO2 were found to strongly adsorb PEO and exhibit flocculation, On the other hand, no significant adsorption was observed on oxides with a point of zero charge (pzc) greater than that of silica such as TiO2, Fe2O3, Al2O3- and MgO thereby indicating specificity of PEG-surface bonding site interactions. The other possible mechanisms of PEO adsorption such as complexation with adsorbed ions and electrostatic interactions with a positively charged surface were found not to play a major role in the PEO adsorption onto oxide particles. In this investigation, the adsorption and flocculation behavior of oxides with PEO and the underlying adsorption mechanism(s) are discussed. (C) 1997 Academic Press.