Two-step assembly (TSA) technique for preparation of polymer- particle composite films is presented. The TSA process consists of coating a polyelectrolyte onto a substrate and dipping the coated substrate in a particle suspension. The previously coated polyelectrolyte acts as a particle aggregation promoter, in other words, as an adhesive for particles. Diffusion and adsorption of the polyelectrolyte are important behaviors for this process. Preparation of composite films consisting of commercially available polyelectrolytes such as poly(diallyldimethylammonium chloride) (PDDA) and colloidal silica (SiO2) or titania (TiO2) particles were demonstrated. The composite films were porous and their thickness depended on the thickness and the molecular mass of previously coated polyelectrolyte, treatment time, and the concentration of suspension. Some PDDA-SiO2 composite films with 190 nm SiO2 particles had colloidal crystal domains and reflected visible light. (C) 2001 Elsevier Science B.V. All rights reserved.
