THE ELECTROKINETIC RESPONSE OF SURFACE-MODIFIED POLYMER LATEXES - EFFECTS OF GRAFTED WATER-SOLUBLE POLYMER AND HEAT-TREATMENT

Low-frequency dielectric spectroscopy and electrophoretic light scattering were used to test the applicability of classical electrokinetic theory to latex particles with and without surface grafted water-soluble polymer. Dielectric measurements on the "hairy" latex reveal large discrepancies between theory and experiment. At the same time, the "bare" latex exhibits qualitatively similar, but smaller, discrepancies. High temperature treatment of the latexes alters the particles and the discrepancies are reduced. The heat-treated bare latex behaves according to the classical theory; the heat-treated hairy latex exhibits greatly reduced deviations from theory. Electrophoretic mobility measurements spanning 2 decades in ionic strength show that the mobilities of the bare and hairy particles converge following heat treatment, suggesting that the surface contrast between the two particles is diminished. A mechanism involving transport processes within a hairy layer is proposed to explain the inadequacy of classical electrokinetic theory with latex particles. © 1992.