A novel layered manganese oxide/poly(aniline-co-o-anisidine) nanocomposite [MnO2/P(An-co-oAs)] was successfully synthesized by a delamination/reassembling process using P(An-co-oAs) ionomer and layered manganese oxide in aqueous solution. This nanocomposite obtained was then characterized by Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), electron microscopy (SEM), and thermogravimetric (TG) analysis. X-ray diffraction and electron microscope analysis showed that the MnO2/P(An-co-oAs) nanocomposite had a lamellar structure with increasing interlayer spacing. The MnO2/P(An-co-oAs) nanocomposite exhibited substantially improved conductivity, which was near 100 times greater than that of its pristine MnO2 (3.5 x 10(-7) S cm(-1)). The specific capacitance of the MnO2/P(An-co-oAs) nanocomposite reached 262 F g(-1) in 1 M Na2SO4 at a current density of 1 A g(-1), which was significantly higher than that of either of its two pristine materials [MnO2 (182 Fg(-1)) or P(An-co-oAs) (127 F g(-1))] owing to the synergic effect between the two pristine components. The fabrication mechanism of the nanocomposite was also proposed and discussed in this paper. (C) 2010 Elsevier Ltd. All rights reserved.