ADSORPTION OF WEAKLY CHARGED POLYELECTROLYTES AT OPPOSITELY CHARGED SURFACES

The adsorption of weakly charged polyelectrolytes at planar and opposi tely charged surfaces was modeled by using a mean-field lattice theory for flexible polyelectrolytes in solution. The nature of the adsorpti on was described in terms of volume fraction profiles, adsorbed amount ; thickness of adsorbed layer, and conformational characteristics at d ifferent salt concentrations. The effect on the adsorption of (i) poly electrolyte length, (ii) linear charge density of the polyelectrolyte, (iii) volume fraction of the polyelectrolyte, (iv) nonelectrostatic p olyelectrolyte-surface interaction, and (v) surface potential or surfa ce charge density, all at different salt concentrations and different surface conditions, was investigated. In most cases, as the salt conce ntration is increased, the adsorbed amount is reduced but the thicknes s of the adsorbed layer is increased. At low salt concentration and at constant surface charge density, the amount adsorbed is governed by t he surface charge density through a polyelectrolyte-surface charge mat ching. At constant surface potential, a more diverse picture has emerg ed. A less regular distribution of the charges along the polyelectroly te chain facilitates the adsorption.