POLYMER ADSORPTION ON FINE PARTICLES - THE EFFECTS OF PARTICLE-SIZE AND ITS STABILITY

The effects of particle size on polyacrylamide(PAAm, M(w) = 59 x 10(4), 500 x 10(4)) adsorption were investigated using a series of well-characterized hematite (alpha-Fe2O3) dispersions. The alpha-Fe2O3 particles with highly monodisperse and nearly spherical shape ranged in radius from 23 nm to 300 nm. The maximum amount of PAAm adsorption(A(m)) in each system, showed a steady increase with decreasing particle radius and was influenced strongly by particle concentrations in the medium. Furthermore, it was realized that the diameter of alpha-Fe2O3 particles after treatment with PAAm under different particle concentrations decreased with increasing particle concentration. The relation between particle concentration in the medium and particle size after treatment was also influenced by the medium pH, i.e., at the medium pH close to the isoelectric point of alpha-Fe2O3 particles (pH-degrees = 9.2), the particle size after treatment increased with increasing particle concentration. All these results suggest that in the system of ultra-fine particles, the mixing process between particle-particle and polymer-particle will play an important role on the conformation of adsorbed polymer layer.