Electrically conductive composites were prepared via the chemical oxidative polymerization of the pyrrole monomer in polystyrene (PS) and zinc neutralized sulfonated polystyrene (Zn-SPS) films under supercritical carbon dioxide (SC-CO2) conditions.The strong swelling effect of SCCO2 made polypyrrole (PPy) particles not only form on the surface,but also become incorporated into the film,resulting in a homogeneous structure with a relatively higher conductivity.By comparison,the composite prepared in aqueous solutions shows a skin-core structure and a conductivity of 3 to 4 orders of magnitude lower than that of the former due to the diffusion-controlled process of the pyrrole monomer.The percolation thresholds of PS/PPy and Zn-SPS/PPy composites were 6.2% and 2.7% of the volume fraction of PPy,respectively,much lower than the theoretically predicted value of 16%.Moreover,the conductive composites prepared under SC-CO2 conditions showed higher thermal stability,especially in the high-temperature region.