Thermoplastic conducting composites of polyparaphenylene diazomethine (PPDA), polythiophene (PTH), poly-3,4-Ethylenedioxythiophene (PEDOT), and polyaniline (PANI) with polyvinylchloride (PVC) and polyurethane (PU) were prepared. Conducting composites were prepared by in situ polymerization of thiophene, ethylene dioxy thiophene, and aniline in the presence of polyvinyl chloride and polyurethane using FeCl3 as the oxidizing agent. PPDA composites were prepared by dispersing PPDA powder in the polymer solution followed by casting. The microwave properties of all the composites were studied in the S band using Vector Network Analyzer and the best composite was selected based on the dielectric properties for microwave applications. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011