On the presence of branching in polyaniline chains

Matnishyan, A. A.; Akhnazaryan, T. L.

doi:10.1134/s1560090407050089

Cited by 6 publications

(9 citation statements)

References 12 publications

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“…The ortho -coupled aniline units can further undergo oxidative cyclization to yield phenazine structures , (Figure ). This type of reaction is well-known from the oxidation of o -phenylenediamine. , or branching and cross-linking reactions in PANI. – Phenazine units can be produced at any point in an oligomer chain.…”

Section: Discussionmentioning

confidence: 99%

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Oxidation of Aniline: Polyaniline Granules, Nanotubes, and Oligoaniline Microspheres

et al. 2008

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Aniline was oxidized with ammonium peroxydisulfate in solutions of strong acid (0.1 M sulfuric acid), weak acid (0.4 M acetic acid), or alkali (0.2 M ammonium hydroxide). The properties of the oxidation products and their morphology are controlled by the initial acidity of the medium and the acidity profile during the oxidation; the acidity increases because sulfuric acid is a byproduct. Conducting polyaniline nanogranules, nanotubes, or nonconducting oligoaniline microspheres were obtained, respectively. FTIR spectra suggest that the oligomers produced by the oxidation of neutral aniline molecules at the beginning of oxidation are similar, regardless of the acidity of the medium. Neutral aniline molecules, prevailing under alkaline conditions, are easily oxidized to aniline oligomers composed of ortho-and para-coupled aniline constitutional units. Orthocoupled units are further converted by oxidative intramolecular cyclization to phenazines. It is proposed that, in acidic media, N-phenylphenazine units constitute the initiation centers for the subsequent polymerization of aniline, which takes place at pH < 2 when the intermediate pernigraniline chains become protonated. Anilinium cations, which dominate in strongly acidic media, are difficult to oxidize to oligomers, but they easily participate in the formation of polymer chains once their growth has started. The self-organization of phenazine units is responsible for the generation of polyaniline nanotubes. Partial sulfonation of aromatic amines occurs at higher pH, especially in alkaline media. The sulfonated oligomers stabilize aniline emulsions and enable the formation of oligoaniline microspheres, when the miscibility of aniline with aqueous medium is limited. The final oxidation products obtained in alkaline conditions contain only low-molecular-weight oligomers; the polymeric component is the dominating product only in strongly acidic media. Both components are present in various proportions when the oxidation takes place at intermediate pH ranges.

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Section: Discussionmentioning

confidence: 99%

“…36,37 or branching and cross-linking reactions in PANI. [38][39][40] Phenazine units can be produced at any point in an oligomer chain.…”

Section: Discussionmentioning

confidence: 99%

Oxidation of Aniline: Polyaniline Granules, Nanotubes, and Oligoaniline Microspheres

et al. 2008

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“…For all previously studied diazonium salts, the reduction of the diazonium cation is severely inhibited in the second scan, while in the case of benzenediazonium investigated here, a slow decrease of the peak current is observed with the number of scans. This implies the formation of a conductive film . It should be noted that this behavior is dependent on the substrate on which the film is grown.…”

Section: Discussionmentioning

confidence: 99%

“…This implies the formation of a conductive film. 43 It should be noted that this behavior is dependent on the substrate on which the film is grown. On carbon, at concentrations lower than 1 mM, the wave keeps a nearly constant height in the second scan 44 and there is little blocking of the electrode.…”

Section: Discussionmentioning

confidence: 99%

Formation of Polyphenylene Films on Metal Electrodes by Electrochemical Reduction of Benzenediazonium Salts

et al. 2006

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It is possible to form micrometer thick polyphenylene (PP) films by electrochemical reduction of benzenediazonium tetrafluoroborate on metals in acetonitrile. The electrochemical behavior of the PP film is characterized by different electrochemical transient methods and is surprisingly different from that observed with other diazonium salts. The films are analyzed by IR and time-of-flight secondary ion mass spectroscopies; their thickness and conductivity are also characterized. Because they are conductive, these micrometer thick films can be further derivatized by electrochemical reduction of other diazonium salts, for example, nitrophenyl or bromophenyl diazonium salts. Copper can also be deposited on the top of the PP film. The behavior of redox probes on PP films is discussed as well as the origin of this increased conductivity. A simple model for the reaction kinetics of electrografting is presented.

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“…The stability of the kation-radical complex with the aniline increases so much in the formic acid that at the initial stage of the synthesis of the aniline it is possible to record the signal electron paramagnetic resonance (EPR) [6].…”

Section: Technical Approachmentioning

confidence: 99%

Synthesis of New Organic Semiconducting Polymer Materials Having High Radiowave Absorption Rate

Matnishyan¹

2008

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On the presence of branching in polyaniline chains

Cited by 6 publications

References 12 publications

Oxidation of Aniline: Polyaniline Granules, Nanotubes, and Oligoaniline Microspheres

Oxidation of Aniline: Polyaniline Granules, Nanotubes, and Oligoaniline Microspheres

Formation of Polyphenylene Films on Metal Electrodes by Electrochemical Reduction of Benzenediazonium Salts

Synthesis of New Organic Semiconducting Polymer Materials Having High Radiowave Absorption Rate

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