An electrolytic admicellar polymerization was chosen for synthesizing new semiconducting nanomaterials composed of sodium montmorillonite (Na+-MMT), polypyrrole (PPy), and natural rubber (NR). The contents of the pyrrole monomer and the Na+-MMT were varied from 100 to 800 mM and 1-7 parts per hundred of rubber (phr), respectively. Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were used to confirm the success of the synthesis. The morphological studies carried out by X-ray diffraction (XRD) and TEM pointed out the different states of dispersion of the layered silicates, whereas the study done by scanning electron microscopy (SEM) showed a great dependence of the nanocomposite morphology on the inclusion of the layered silicates. Thermal stability studies demonstrated the thermo-protecting and thermo-oxidative behaviors imparted by the layered silicates. The mechanical and DC electrical conductivity properties were significantly improved with the inclusion of the layered silicates, especially at a 7 phr loading. (C) 2009 Elsevier Ltd. All rights reserved.