Poly(methacrylic acid) adsorption and electrical surface properties of titanium dioxide suspensions

Abstract

The influence of adsorbed poly(methacrylic acid) (PMAA) of molecular weight 10 × 103 on the aggregation stability of titanium dioxide suspensions and on the zeta potential of the particles has been studied over a wide range of pH (from 2.0 to 12.0). The dependence of the zeta potential of titanium dioxide particles in aqueous suspension on the pH of the system was typical for metal oxides and passed through an isoelectric point at pH0 = 6.2. Adsorption of poly(methacrylic acid) on to titanium dioxide particles had a considerable effect on the dependence of the zeta potential of the particles on the pH of the suspension medium. The change of zeta potential both in the absence and presence of PMAA correlated well with the aggregation stability of the suspensions, which was estimated from the mean radius of the particles. The influence of the adsorbed poly(methacrylic acid) macromolecules on the zeta potential of the particles can be explained according to a scheme which envisages both a decrease in the particle surface potential and a change in the potential distribution in the electrical double layer.