Preparation of oxide dispersions which are stabilized both sterically and electrostatically

TiO2 dispersions prepd. in the presence of poly(acrylic acid) (I) may be sterically stabilized, electrostatically stabilized, or stabilized by both mechanisms simultaneously, depending on I and electrolyte concns. Very stable suspensions are obtained when both steric and electrostatic stabilizations occur. I adsorption is esp. pronounced at low pH, when TiO2 and I are oppositely charged. Larger amts. of I are effectively adsorbed as neutral mols., since the large concn. of anionic groups near the TiO2 surface causes a large neg. elec. potential which exerts a strong attraction on H+ ions. The thickness of the I layer is about 3 nm at pH = 6 in 0.01 M KNO3 solns. The results of the expts. suggest that both mechanisms are important and that there is a pos. influence of the thin polymer layer on the electrostatic stabilization. [on SciFinder (R)]