Copper nanoclusters were synthesized by a chemical reduction of an aqueous copper salt solution by sodium borohydride. A polyaniline nanocomposite containing copper nanoclusters was prepared by polymerizing a monomer aniline hydrochloride solution containing the copper nanoclusters using ammonium persulfate as an oxidizing agent. The synthesized nanocomposite was characterized using various techniques such as UV-visible spectroscopy, FTIR spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The presence of copper was confirmed by XRD and the size of the copper clusters was found to be similar to53 nm, which is in good agreement with that obtained from the TEM. The synthesized nanocomposite was used to serve as a catalyst in a Wacker oxidation reaction for the conversion of 1-decene to 2-decanone in the presence of molecular oxygen. The formation of 2-decanone was confirmed using GC-MS. (C) 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2412-2417, 2003.