Poly(pyridylureas) and poly(pyridylthioureas) were synthesized by reacting 2,6-diaminopyridine with phosgene and thiophosgene, respectively, using THF and pyridine as solvent. The synthesized polymers were characterized by IR-spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy. Thermal stability of the polymers was determined by thermal degradation between 35 degrees C and 700 degrees C The 50% weight loss of polypyridylureas was above 400 degrees C while for the polypyridylth-ioureas it was above 450 degrees C. Undoped poly(pyridylureas) and poly(pyridylthioureas) behave as semiconductors, a = 10(-9) (Omega cm)(-1). After doping with 12 and SbF5, the electrical conductivity increases several orders of magnitude, sigma = 10(-7)(Omega cm)(-1). (c) 2007 Wiley Periodicals, Inc.