INFLUENCE OF ELECTROLYTES ON THE ADSORPTION OF POLYVINYL-ALCOHOL) ON POLYSTYRENE PARTICLES AND ON THE STABILITY OF THE POLYMER-COATED PARTICLES

The effect of electrolyte type (KCl, Na2SO4, and CaCl2) on the adsorption isotherm of poly(vinyl alcohol) onto polystyrene latex particles from aqueous solution at 25°C has been investigated, together with complimentary measurements on the polymer dimensions in free solution. Slow-speed centrifugation studies on these systems were also carried out. The results show an increase in amounts adsorbed with increasing electrolyte concentration, the effect being most marked with Na2SO4 and least with CaCl2. There is some evidence for steps in the adsorption isotherms at high polymer concentrations. With increasing electrolyte concentration there appears to be only a small decrease in the polymer dimensions in free solution and little or no change in the adsorbed layer thickness, at least at low electrolyte concentrations. At high electrolyte concentrations, approaching the critical flocculation electrolyte concentration (CFC), there seems to be significant interpretation and/or compression of the adsorbed layers under the weak centrifugal field applied. The CFC at 25°C was found to be 1.27 mole dm-3 for KCl and 0.175 mole dm-3 for Na2SO4. No flocculation was detected in the case of CaCl2, at least up to a concentration of 3 moles dm-3. © 1979 Academic Press, Inc.