Chemical nature of the nitrogens in polypyrrole and nitrogen-substituted polypyrrole: a comparative study by X-ray photoelectron spectroscopy

Abstract

The chemical nature of the nitrogens in polypyrrole (PPY) and poly(N-methylpyrrole) (PMPY) has been critically compared using X-ray photoelectron spectroscopy as a primary tool. Treatment of PPY/perchlorate complex with NaOH results in a deprotonation process which gives rise to a PPY base (DP-PPY) having an intrinsic oxidation state consisting of 25% oxidized imine-like (=N-) structure, similar to that observed in the 50% oxidized emeraldine state of polyaniline. This intrinsic oxidation state, however, does not exist in the nitrogen-substituted PPY. As a result, the charge-transfer (CT) mechanisms involving the two base polymers and the various oxidants and electron acceptors are vastly different. The PMPY base undergoes strong CT interactions with metal oxidants, such as Cu(ClO4)2, but interacts only weakly with organic electron acceptors, such as the halobenzoquinones and cyanobenzoquinones. The reverse is true for DP-PPY. Both polymer complexes also exhibit different thermal degradation behaviour. © 1992 Chapman & Hall.