Processibility is one of the important requirements for the commercial utilization of conducting polymers. Studies on composites and blends based on nano polyaniline (PANI) dispersions have become the subject of scientific curiosity with regard to their morphology, stability, and electron transport properties. In general, polymer nanocomposites are made by dispersing inorganic or organic nanoparticles into either a conventional thermoplastic or thermoset polymer. The present study reports the synthesis of nanostructured MO-PANI and castor oil polyurethane (COPU)-based composites. The effect of loading of nanostructured MO-PANI in COPU on the spectral, physicochemical and morphological properties has been analyzed. (C) 2009 Wiley Periodicals, Inc. Adv Polym Techn 28: 26-31, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20143