This study covers the synthesis of homopolymers, copolymers and composites of aniline and pyrrole in nitrogen atmosphere using various solvent and supporting electrolytes. With the objective of examining the structure of the samples and analysing their properties, FT-IR spectra were taken, thermogravimetric analysis (TGA) was done and scanning electron microscopy (SEM) was used for microstructural analysis. The conductivity of each sample was determined through the four-probe method. Magnetic susceptibility measurements on the Gouy scale indicated that the polymers were diamagnetic. Hence, the synthesized polymers were found to contain no unpaired electrons. Homopolymerization and copolymerization reactions were carried out in an acetonitrile medium, using LiClO4, as supporting electrolyte, in a perchloric acid medium and in a sulfuric acid medium separately, in order to analyse the effects of solvent and supporting electrolytes. As a result, the change of medium was observed to have a significant effect on the structure and properties of the resulting homopolymers. Similarly, in bilayer synthesis, changing the order of coating was observed to affect the structure and properties of samples, either partially or fully, based on the synthesis medium. For instance, coating polyaniline (PAn) over polypyrrole (PPy) in an acetonitrile + LiClO4 medium or a water + H2SO4 medium yielded composite samples, while coating PPy over PAn in the same media yielded copolymer samples. The resulting samples however, turned out to be composites regardless of the order of coating, when the same synthesis was repeated in a HClO4 medium. (C) 1998 Elsevier Science S.A. All rights reserved.