Role of p-Benzoquinone in the Synthesis of a Conducting Polymer, Polyaniline

Abstract

Polyaniline (PANI) and 2,5-dianilino- p -benzoquinone both are formed by oxidation of aniline in an acidic aqueous environment. The aim of this study is to understand the impact of addition of p -benzoquinone on the structure of PANI prepared by the oxidation of aniline hydrochloride with ammonium peroxydisulfate and to elucidate the formation of low-molecular-weight byproducts. An increasing yield and size-exclusion chromatography, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy, and nuclear magnetic resonance analyses of the products show that p -benzoquinone does not act as a terminating agent in the synthesis of PANI and the content of 2,5-dianilino- p -benzoquinone increases with the increasing molar concentration of p -benzoquinone in the reaction mixture, [BzQ]. Regarding the structure of PANI, Raman and UV–visible spectra show that the doping level and the charge delocalization both decrease with the increase of [BzQ], and the FTIR spectra of the PANI bases indicate an increased concentration of benzenoid units at higher [BzQ]. We explain these observations by an increasing concentration of structural defects in PANI chains and propose a 2,5-dianilino- p -benzoquinone-like structure of these defects present as pendant groups. The bands typical of 2,5-dianilino- p -benzoquinone-like moiety are observed even in the vibrational spectra of the sample prepared without addition of p -benzoquinone. This confirms in situ oxidation of aniline to p -benzoquinone within the course of the oxidation of aniline hydrochloride to PANI.

Synthesis and Impedance Spectroscopy of Poly(p-phenylenediamine)/Montmorillonite Composites

“…However, let us mention the peak at 1656 cm −1 in the spectrum of PPDA-50. We suspect this band can be related to C=O stretching of the benzoquinone structure [ 37 , 38 , 39 ].…”

Vitamin C assisted synthesis of rGO–Ag/PANI nanocomposites for improved photocatalytic degradation of pharmaceutical wastes

“…31 Moreover, the C-N stretching vibration of quinoid and benzenoid rings are shown at 1385 cm À1 and 1328 cm À1 , respectively. 32 The N-H bending bands (1304 cm À1 , 1210 cm À1 and between 1515-1520 cm À1 ), and nitro group of onitroaniline due to asymmetric and symmetric stretching (1510 and 1346 cm À1 ) are also detected. 33 The rGO-Ag/PANI shows the peak due to PANI and rGO; however, the band positions and intensities are found to differ.…”

Long range self-organisations of small metallic nanocrystals for SERS detection of electrochemical reactions

“…At this stage it is difficult to identify clearly the additional product detected at +0.10 V. In the literature, at oxidizing potentials 4-ATP may be oxidized to radicals that subsequently couple [45]. Also, during chemical oxidation of aniline to polyaniline, production of benzoquinone moieties have been evidenced, with a signal appearing at 1650 cm −1 [46]. One possibility is thus that coupling of reacting intermediates or/and 4-ATP within the NCs matrix produces oligomers that are Fig.…”