Spectroscopic Characterization of Oligoaniline Microspheres Obtained by an Aniline−Persulfate Approach

Abstract

This paper investigates the structure of the products obtained from the polymerization of aniline with ammonium persulfate in a citrate/phosphate buffer solution at pH 3 by resonance Raman, NMR, FTIR, and UV-vis-NIR spectroscopies. All the spectroscopic data showed that the major product presented segments that were formed by a 1,4-Michael reaction between aniline and p-benzoquinone monoimine, ruling out the formation of polyazane structure that has been recently proposed. The characterization of samples obtained at different stages of the reaction indicated that, as the reaction progressed, phenazine units were formed and 1,4-Michael-type adducts were hydrolyzed/oxidized to yield benzoquinone. Raman mapping data suggested that phenazine-like segments could be related to the formation of the microspheres morphology.

The First Products of Aniline Oxidation – SERS Spectroelectrochemistry

“…Neither meet their views on the PANI films formation. Chemically prepared PANI films are reported to contain a layer of ortho‐coupled oligomers ( o ‐AO, Figure a), although they sometimes are too thin to detect . Chemists believe these oligomers are necessary for the film formation because they have been observed in every film‐formation study with only one exception .…”

“…Properties of the thin layer in direct contact with the substrate are difficult to study but the existence of a different layer between the substrate and the chemically prepared PANI film was proven by ellipsometry, Raman spectroscopy and X‐ray photoelectron spectroscopy . The molecular structure of o ‐AO is still widely discussed, various branched, quinonoid, benzoquinonoid and phenazine‐like structures have been proposed . In fact, o ‐AO is a mixture of species containing the above‐mentioned structural units, however, N‐phenyl‐phenazinium cation based o ‐AO (Figure a, first structure) are believed to be the ones responsible for film formation …”

Identification of dyes in toned and tinted XX century cinematographic films by surface enhanced Raman spectroscopy

“…d and S3). Two strong features at 1556 and 1638 cm −1 are attributed respectively to the CC stretching–HCC bending and to the HNH bending–CC stretching phenazine aromatic modes of the phenazine moiety, while the bands at 616 cm −1 and 1376 cm −1 are because of CCC bending and CC stretching phenazine aromatic modes, which are associated with the presence of phenazine‐like segments …”

“…The band at 1124 cm À1 corresponds to the out-of-plane CH deformation of the phenyl rings. [26] In sample IMB2, comparison with data reported in literature [30,31] allows to identify the presence of safranin. This dye, whose molecular structure is shown in Fig.…”

“…In sample IMB2, comparison with data reported in literature allows to identify the presence of safranin. This dye, whose molecular structure is shown in Fig.…”