XPS studies of proton modification and some anion exchange processes in polypyrrole

Abstract

The N(1s) X-ray photoelectron spectroscopy (XPS) core-level spectrum reveals that proton modifications of the nitrogens in polypyrrole (PPY) can give rise to a number of intrinsic redox states, as in the case of the nitrogen in polyaniline. In PPY, these states can range from that consisting of about 25% oxidized neutral imine-like (=N-) structure observed in this study, to that consisting entirely of reduced amine-like (-NH-) structure or PPY0. The former is obtained by deprotonation of the oxidized and positively charged pyrrolylium nitrogens (-N+H- structure) while the latter is obtained via the reduction of the deprotonated polymer by phenylhydrazine. Protonation of the deprotonated units by acids or oxidation of PPY0 by electron acceptors returns the polymer to its oxidized and positively charged state. The oxidized PPY/halide and PPY/p-chlonil complexes readily undergo anion exchange in protonic acid media or in organic solvents containing an electron acceptor of higher electron affinity than the original oxidizing anion. The anion exchange processes offer an alternative chemical route for the preparation of some conductive and anion specific PPY complexes. © 1990.