| Abstract
| - The adsorption of poly(vinylamine) (PVA) on poly(styrene sulfate) latex particles is studied, and itsconsequences on the charging behavior and suspension stability are investigated. The adsorption processis assessed by batch depletion experiments and time-resolved electrophoretic mobility measurements. Theadsorption of PVA appears to be basically irreversible. The rate of adsorption decreases with decreasingpolymer dose. At low polymer dose, the polymer coverage corresponds to the amount of the polyelectrolyteadded, while at high polymer dose, the polymer coverage saturates the surface. Stability ratios are determinedby dynamic light scattering, and strongly depend on the polymer dose and salt level. The aggregation israpid near the isoelectric point (IEP), and it slows down when moving away from it. The charge neutralizationis highly nonstoichiometric with charging ratios (CR) larger than unity, meaning that several charges onan adsorbed polyelectrolyte chain are necessary to neutralize a single charge on the particle surface. Bycomparing the IEP for particles and polyelectrolytes of different charge densities, we find a strong dependenceof the CR on the mismatch between the average distances between individual charges on the surface andon the polyelectrolyte. A simple model is proposed to explain this trend.
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