XPS AND ESR STUDIES OF ELECTROCHEMICALLY SYNTHESIZED POLYCARBAZOLE POST-DOPED WITH IODINE

Polycarbazole powders obtained by electrochemical oxidation of carbazo le thin films or of carbazole in solution in the electrolyte have been post-doped with iodine and characterized by room temperature electric al conductivity, X-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR). Similar results are obtained with polymers satur ated with iodine at room temperature after 6 weeks and with polymers d oped at 383 K for 24 h. The polymers obtained from carbazole thin film s have a higher electrical conductivity (sigma similar to 10(-4) Omega (-1) cm(-1)) and a higher spin density (9.9 10(21) spins mol(-1) g(-1) ), which corresponds to 71 atom % of ionic iodine. The polymer radical s are located on the nitrogen, and the percentage of N+ is 40 atom %. The electrical conductivity of the polymers obtained from carbazole in solution in the electrolyte is two order of magnitude smaller. The pe rcentage of N+ is only 25 atom % with an ionic iodine percentage of 13 atom %. So, the most important parameter is not the iodine percentage introduced after doping into the polymers but the percentage of ionic iodine present in the polymers. The differences that are put in evide nce can be explained by a better polymerization efficiency of the carb azole when it is deposited on thin film form by vacuum evaporation bef ore electrochemical oxydation. (C) 1999 John Wiley & Sons, Inc.