Aniline monomer was dispersed in polymethyl methacrylate (PMMA) and polyvinyl carbazole (PVK) solutions. The resulting mixtures were coated on substrates, dried in toluene atmosphere and enclosed later on in a chamber containing an oxidized atmosphere of HCl and (NH4)(2)S2O8. Electrical and optical characterizations indicate that polyaniline (PANI) was formed in the PMMA and PVK matrixes. Sheet resistance as a function of the pH value demonstrates that both PANI-PMMA and PANI-PVK composite coatings keep their R-square almost unchanged when they are immersed in a moderate basic solution (pH similar to 9). Especially, PANI-PVK coatings are more stable than PANI-PMMA samples for longer time of immersion and also in solutions with a higher pH value, Scanning electron micrographs show different surface morphologies of these two composite materials suggesting a possible explanation of their chemical stability.