Thermally stable bentonite-polybenzimidazole (PBI) nanocomposites were synthesized from reactive organoclay and polybenzimidazole. The reactive organoclay was formed by using hexadecylpyridinium chloride (CPC) as a swelling agent for silicate layers of bentonite. The swelling process was carried out through ion exchange reaction between the end group of hexadecylpyridinium chloride salt and the sodium ion in bentonite. This irreversible swelling monitored by measuring the cation exchange capacity (CEC) of the bentonite solutions. Dispersion of the modified clay in the polybenzimidazole matrix resulted in nanostructured material containing intercalated polymer between the silicate layers. X-ray and thermal analysis confirmed structure of the now hybrid materials. The glass transition temperature and the thermal decomposition temperatures of this type bentonite-PBI were found to be higher than that of pure PBI. (C) 2003 Elsevier B.V. All rights reserved.