Adsorption of a low-molecular-weight polyacrylic acid on silica, alumina, and kaolin

Polyelectrolytes are often used to prepare highly concentrated dispersions of particles of heterogeneous surfaces of controlled viscosity and stability. However, there is not a satisfactory understanding of the adsorption mechanism of polymers on the surface of heterogeneously charged particles such as kaolin. A systematic investigation of the interaction of silica, alumina, and kaolin, with Na-polyacrylic acid (PAA) polyelectrolyte was performed by conducting adsorption experiments and employing attenuated total reflection infrared spectroscopy (FTIR/ATR) techniques. Adsorption studies indicate that the adsorption density of Na-PAA on the surface of kaolin is considerably smaller than that on alumina particles and there is no indication of adsorption of PAA on the surface of silica particles. FTIR/ATR experiments confirmed that there are specific interactions between PAA and the surface of alumina and kaolin particles as the adsorption bands are shifted to higher wavenumbers. (C) 2002 Elsevier Science (USA).