Multilayer thin films based on polyelectrolyte-complex nanoparticles

Polyelectrolyte complex nanoparticles, obtained by mixing two solutions of oppositely charged polyelectrolytes in non-stoichiometric ratios, were assembled into multilayer films on flat substrates by their alternate adsorption with oppositely charged polyelectrolyte. The incorporation of these nanoparticles in thin films was examined by UV-vis spectroscopy, quartz crystal microgravimetry and atomic force microscopy. The observed film thickness is up to 45% larger than films conventionally prepared from uncomplexed polyelectrolytes (for the same number of adsorption cycles), yielding an average thickness of approximately 40 nm for a ten layer film. The system presented here provides a viable approach to prepare thick polyelectrolyte-based films of defined composition, with potentially different permeability and mechanical characteristics than their layer-by-layer assembled polycation/polycation film counterparts. (C) 2002 Elsevier Science B.V. All rights reserved.