Aniline oligomers versus polyaniline

Abstract

This paper deals with aniline oligomers produced by the oxidation of aniline with ammonium peroxydisulfate under alkaline conditions. Oligomers obtained in 1 mol L −1 ammonium hydroxide as microspheres have been analyzed. They are brown, non-conducting, and are composed of tens of aniline constitutional units. They contain oxygen in semiquinonoid and quinonoid constitutional units or both, and sulfur in sulfonic or sulfate groups. Phenazine-like units in the oligomers have been identified by UV-visible spectra and the IR spectra support them. IR spectroscopic analysis of fractions insoluble and soluble in chloroform suggests that aniline oligomers are not uniform and strong hydrogen bonding occurs in their structure. Aniline oligomers will be potentially useful in applications that do not require conductivity but use the redox or salt-base transitions typical of polyaniline. Their applicability is illustrated by the ability to reduce silver cations to silver, base-salt transitions and in the carbonization to nitrogen-containing carbons.

Carbonization of aniline oligomers to electrically polarizable particles and their use in electrorheology

“…A prominent band at 824 cm À1 in the substitution region 900-650 cm À1 in the spectrum of the PANI base is due to the C-H out-of-plane bending vibrations of dominating para-coupled constitutional units. The bands at 746 and 691 cm À1 correspond to the C-H out-of-plane bending and out-of-plane ring deformations of a mono-substituted phenylene ring, respectively [24,36]. The spectrum of the oligomers displays bands at 3440 and 3324 cm À1 of asymmetric and symmetric free N-H stretching vibrations, supporting the contribution of the N-H scissoring vibration.…”

“…The peaks at 3266 and 3195 cm À1 corresponding to the hydrogen-bonded N-H vibrations are detected in the spectrum of aniline oligomers. They are connected with hydrogen bonding of N-H groups with sulfonic or carbonyl groups [24]. The infrared spectra of samples prepared in 0.1 M NH 4 OH and in water display a broad absorption band at wavenumbers higher than 2000 cm À1 , an increased absorption of the bands at 1300 and 1238 cm À1 , and a broad band centred at 1144 cm À1 , which are characteristic of the conducting protonated form of polyaniline [36].…”

“…Two hydrogen atoms are abstracted from each aniline molecule during their oxidative coupling, and they are released as protons; thus, the pH of the reaction mixture decreases (Fig. 2) [24].…”

“…Conducting PANI is produced by the oxidation of aniline with ammonium peroxydisulfate under acidic conditions. When oxidation of aniline is started under alkaline conditions, nonconducting aniline oligomers are produced as microspheres of several micrometres in diameter [24]. Their molecular structure is open to discussion but it is assumed that they are represented by condensed aniline molecules including oxygen atoms resulting from hydrolytic processes (Fig.…”

Smart nanomaterials based on the photoactivated release of silver nanoparticles for bacterial control

“…68 However, studies have shown the ability of modulate the inflammatory responses in human fibroblast, 70 since, amino groups can be protonated and in the presence of proton ions that are released in the inflammatory area, resulting in a analgesic effect. 72 It is an electroactive compound, with photoelectrocatalityc degradation 73 . The unshared electron pair on the aniline is delocalized and therefore less available to donate.…”