Adsorption of Polyampholytes on Polystyrene Latex: Effect on Colloid Stability

Abstract

The interfacial characteristics of low-charge-density polyelectrolytes and polyampholytes synthesized by a microemulsion polymerization technique have been investigated. Terpolymers of acrylamide (AM, neutral segment), [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MADQUAT, positively charged segment), and sodium 2-(acrylamido)-2-methyl propanesulfonate (NaAMPS, negatively charged segment) and copolymers of AM and MADQUAT as well as of MADQUAT and NaAMPS were adsorbed on a negatively charged polystyrene latex. The zeta potential at full surface coverage was determined and analyzed as a function of the surface charge excess of the colloid–polymer complex. The domains of colloidal instability were determined and the rate of destabilization was studied for the different systems at the optimum flocculation concentration. A deviation from the usual polyelectrolyte behavior was found for the copolymers and the terpolymers, which may be attributed to the reversible character of the aggregation processes resulting from a progressive modification of the characteristics of the adsorbed layer.