Infrared Investigations of Pristine Polypyrrole - Is the Polymer Called Polypyrrole Really Poly(Pyrrole-Co-Hydroxypyrrole)

Polypyrrole Ppy is one of the most extensively investigated of the electronically conductive polymers. Nevertheless, there is still much we dont understand about this interesting and useful material. One of the most persistent mysteries involves simple chemical composition. Doped PPy should have the empirical formula C4 H3 NX where X is the dopant counterion and z is the fractional doping level z is typically on the order of 0.3. However, elemental analyses of PPy typically show empirical formulas like C4 H3 NXzOy where y ranges from 0.3 to 0.7 unaccounted for oxygen atoms per pyrrole ring. This paper presents IR spectral data which suggests that the oxygen in PPy is present as covalently-bound hydroxide. Analogous IR investigations of polyN-methylpyrrole films show that this polymer is also hydroxylated. The hydroxy substitution present in these polymers undoubtedly results from nucleophilic attack by water on the nascent polycationic chains.