Thermal degradation studies of perchlorate-doped conductive polymers

Abstract

The thermogravimetric behavior of polypyrrole (PPY), polybithiophene (PBT), and polyaniline (PAN) perchlorate complexes and their corresponding base polymers have been studied. The PBT-perchlorate complex and base polymer decompose at significantly lower temperatures than do the PPY and PAN counterparts. All three perchlorate complexes retain half or more of their original conductivities with no changes in the doping levels after one cycle of heating to 150°C in air and cooling to room temperature. However, after heating at 150°C for 24 h, only the PAN-perchlorate complex shows no significant change in the doping level, although its conductivity decreases by more than two orders of magnitude. X-ray photoelectron spectroscopy analyses of the perchlorate complexes reveal the presence of at least two distinct chlorine species. The thermal decomposition of the perchlorate anions results in the formation of volatile chlorine species as well in chlorine covalently bonded to the polymer. The thermal decomposition of the PPY-perchlorate complex also results in the conversion of positively charged nitrogens to iminelike structures.