In this study, we prepared a series of polymer-clay nanocomposite (PCN) materials that consisted of an emeraldine base of poly(o-methoxyaniline) and layered montmorillonite. Organic o-methoxyaniline monomers were first intercalated into the interlayer regions of organophilic clay hosts followed by a one-step in situ oxidative polymerization. The as-synthesized PCN materials were subsequently characterized by FTIR spectroscopy, wide-angle powder X-ray diffraction, and transmission electron microscopy. The molecular weights of PMA extracted from PCN materials and bulk PMA were determined by GPC with THF as eluant. Effects of the material composition on the thermal stability, flame resistance, electrical conductivity, and corrosion inhibition performance of PMA, along with a series of PCN materials in the form of fine powder and coating, were also studied by TGA, limiting oxygen index measurements, four-point probe technique, and electrochemical corrosion measurements, respectively. Morphological images of as-synthesized materials were also investigated by SEM. (C) 2003 Wiley Periodicals, Inc.