Mean-field theory and scaling arguments are presented to modelpolyelectrolyte adsorption from semi-dilute solutions onto charged surfaces.Using numerical solutions of the mean-field equations, we show that adsorptionexists only for highly charged polyelectrolytes in low salt solutions. Simplescaling laws for the width of the adsorbed layer and the amount of adsorbedpolyelectrolyte are obtained. In other situations the polyelectrolyte chainswill deplete from the surface. For fixed surface potential conditions, the saltconcentration at the adsorption--depletion crossover scales as the product ofthe charged fraction of the polyelectrolyte f and the surface potential, whilefor a fixed surface charge density, \sigma, it scales as \sigma^{2/3}f^{2/3},in agreement with single-chain results.
展开▼
