The electrochemical polymerization of aniline on a platinum electrode in aqueous HClO
4 and H
2SO
4 solutions has been studied by means of
in situ Fourier-transform infrared (FTIR) reflection spectroscopy. The spectra, taken at early stage of the polymerization in both solutions, exhibited the absorption characteristic of polyaniline (PAn) in an emeraldine state, even at a highly positive potential (≥+0.7 V
vs. Ag/AgCl (saturated KCl)). Polymer growth in H
2SO
4 was accompanied by an increase in the molar ratio of [HSO
4-]/[SO
42-], indicating that the protons generated during the oxidation of aniline react with SO
42- to afford HSO
4-, and that polymer growth is facilitated. In contrast, such proton-scavenging behavior was not observed in a HClO
4 solution, and the growth of PAn was suppressed owing to the accumulation of protons. Under the condition that aniline was extremely consumed, the produced PAn was subjected to oxidative degradation, which was competitive with the growth process of PAn. The major degradation species was identified to be
p-benzoquinone.
抄録全体を表示