Supercritical carbon dioxide, saturated with pyrrole, was brought into contact with oxidant-impregnated films of poly(chlorotrifluoroethylene) (PCTFE), crosslinked poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), and porous crosslinked polystyrene (PS) in order to form conducting composites via the in situ polymerization of pyrrole. The two nonporous hosts-PCTFE and crosslinked PDMS-did not form conducting composites with polypyrrole (PPy). On the other hand, the electrical conductivity of the PPy composites with carbon dioxide-swollen PMMA and porous PS ranged from 1.0 X 10(-4) S/cm to 3.0 X 10(-5) S/cm. In these two cases, the level of pyrrole polymerized on the surface or in the pores of the host polymer was sufficient to attain the interconnected conducting polymer networks necessary for electrical conductivity. (C) 2003 Whiley Periodicals, Inc.