Thermal degradation of leucoemeraldine, emeraldine base and their complexes

Abstract

Themiogravimetric scans of leucoemeraldine in N2 revealed minimal weight changes below 400°C. The initial stages in the degradation of leucoemeraldine involved the loss of some hydrogen, resulting in the formation of imine-like structures. The presence of these structures was confirmed by IR absorption spectroscopy and X-ray photoelectron spectroscopy. The presence of high O2 concentration and elevated temperatures accelerated the formation of the imine structures. Emeraldine base showed slightly higher thermal stability in N2 than leucoemeraldine. In air, volatile oxidation products were formed from both leucoemeraldine and emeraldine base above 350°C. The thermal stability of acid protonated emeraldine depended to a large extent on the protonating add. With HCl and H2SO4 as protonating acids, absorbed moisture accounted for an initial weight loss of ca. 10% upon heating to 100°C, and the loss of the protonating acid species commenced above 250°C. The degradation of the halobenzoquinone complexes of leucoemeraldine and emeraldine was initiated by the decomposition of the incorporated organic acceptor. © 1990.