Poly(N-hydroxypyrrole) and poly(3-phenyl-N-hydroxypyrrole): synthesis, conductivity, spectral properties and oxidation

Costas Kakouris, Joe A. Crayston*, John C. Walton

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

N-Hydroxypyrrole and 3-phenyl-N-hydroxypyrrole were oxidized by (ButO2) in the presence of light to give the transient pyrrolyl-1-oxyl (nitroxide) radicals which were observed by EPR spectroscopy. The corresponding poly(N-hydroxypyrroles) were prepared by chemical oxidation with ferric salts, or, in the case of N-hydroxypyrrole only, by electrochemical oxidation in CH3CN at + 1.2 V versus SCE. The latter polymer had a considerably higher electronic conductivity than the chemically produced polymers (10-4 cf. 10-10 S cm-1), but much lower conductivity than polypyrrole prepared via the same route. It is not clear from the FT-IR spectra of these polymers whether the hydroxyl group survived intact, or whether it was converted back to the amine. Microanalyses showed that the electropolymerized materials had the expected formulation, but chemical polymerization with FeCl3 led to the introduction of one O per monomer unit in the case of pyrrole, and two and three O atoms, respectively, for FeCl3- and Fe(NO3)3-polymerized N-hydroxypyrroles. The EPR spectrum of each polymer consisted of a single featureless band at g = 2.003. The poly(N-hydroxypyrroles) were further oxidized by PbO2 and m-chloroperbenzoic acid (MCPBA) to give polymer containing a strong band at 1720 cm-1 which may be due either to a ketone group (e.g. pyrrolidone) or possibly an oxoammonium (>N+O) species. Microanalyses showed that while electropolymerized polypyrrole had been oxidized by one O atom per monomer, the chemically prepared polymers (FeCl3) had been oxidized up to the same level as the ferric nitrate-prepared polymers (i.e. from two to three O per pyrrole unit). These oxidized polymers were effectively insulators.

Original languageEnglish
Pages (from-to)65-77
Number of pages13
JournalSynthetic Metals
Volume48
Issue number1
DOIs
Publication statusPublished - 15 Jun 1992

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