Influence of the ionic strength on the structure of polyelectrolyte films at the solid/liquid interface

The structure of polyelectrolyte multilayers built up by alternate adsorpti on of polyanions and polycations is investigated by X-ray reflectivity at t he solid/air and neutron reflectivity at the solid/liquid interface. The ex periments provide detailed information about the density gradient of polyel ectrolyte chains across the film and show the influence of the water conten t of the film on the internal structure. The polyelectrolyte density is det ermined by the adsorption conditions (e.g. amount of NaCl) and cannot be ch anged by addition of salt after adsorption. After drying the film thickness is reduced by 30%. (C) 2000 Elsevier Science B.V. All rights reserved.