Sorption of poly(vinyl alcohol) and its cationic derivative on silica oxide: effect of charge

Adsorption of poly(vinyl alcohol)-based cationic polyelectrolyte (DEAE-PVA) as well as unmodified poly(vinyl alcohol) (PVA) onto silica oxide surface was studied by means of reflectometry. The study was focused on the effect of charge of polymer segments on their adsorption on silica oxide. The results showed that the adsorption rate depended on the polymer concentration and was significantly higher for polyelectrolyte than for unmodified PVA. The maximum adsorbed value at the same pH did not depend on polymer concentration. The adsorption of both polymers on silica oxide was highly affected by pH. To explain the reasons, the zeta potential of the silicagel surface as well as of the polymers was measured. The highest sorption of DEAE-PVA was reached at pH above 6 when the gel surface and DEAE-PVA were charged oppositely. It was presumed that the DEAE-PVA adsorption was strongly affected by the electrostatic interaction between dissociated silanols and amino groups of the polymer. The coated silica oxide surface was characterized by atomic force microscopy. The water contact angles showed that the coated surfaces were more hydrophilic and possessed better wetting abilities than the surface of uncoated silica oxide