Mechanism of electrochemical reactions of polyaniline films formed under the conditions of cathodic oxygen reduction

Zhuzhel’skii, D. V.; Krylova, V. A.; Ivanov, V. D.; Malev, V. V.

doi:10.1134/s1023193509020049

Cited by 5 publications

(4 citation statements)

References 19 publications

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“…Obviously, in the absence of other strong oxidants (with an oxidation potential higher than +1.05V), phenazine ring is oxidized with atmospheric oxygen whose oxidation potential is equal to +1.23 V; in addition, oxygen is soluble in water and is therefore accessible for the reactants. The formation of traces of polyaniline by the action of oxygen was reported in [59][60][61][62]. We believe that just atmospheric oxygen triggers the transition from oligomerization to polymerization, i.e., propagation of regular polyaniline chains, in the oxidation of aniline with weak oxidants.…”

Section: Polymerization Initiation Centermentioning

confidence: 92%

Oxidation of aniline with strong and weak oxidants

Sapurina

Stejskal

2012

Russ J Gen Chem

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Oxidative polymerization of aniline by the action of a strong oxidant, ammonium peroxodisulfate, and a weak oxidant, silver nitrate, was studied in media with different acidities. Depending on the reaction conditions, the organic fraction of the products contained either nonconducting aniline oligomers or conducting high-molecular polyaniline. The effect of the oxidation potential on the oxidation process and formation of supramolecular structures by oxidation products was discussed on the basis of analysis of the kinetics and products of aniline oxidation by spectroscopic, conductometric, thermogravimetric, chromatographic (gel permeation), and electron microscopic methods. A relation was revealed between the morphology of composite materials and their electric conductivity.Oxidation of aniline gives rise to numerous useful products such as drugs, dyes, explosives, and polymeric materials. Polyaniline (PANI) obtained by oxidative polymerization of aniline is among the most widely known representatives of conducting polymers. Polyaniline has found practical applications due to its redox and acid-base properties, high thermal stability, and electric conductivity. It is used in energy-saving devices and sensors, for electromagnetic shielding, and for the preparation of antistatic and conducting coatings; it also acts as corrosion inhibitor. Polyaniline possesses a high potential for use in medicine and heterogeneous catalysis [1].Polyaniline is synthesized by oxidation of aniline in aqueous or aqueous-organic medium. Polymerization of aniline is a chain process, i.e., monomer units are successively appended to a polymer chain bearing an active terminal group. Wei [2] considered aniline polymerization to be a specific reactivated chain process. Chain propagation involves repeated activation-deactivation acts which imply oxidation-reduction. Inactive polymer chain is activated by the action of oxidant, but the subsequent reaction with monomer leads to reversible reduction and deactivation. During the reduction process, polymer chain extends due to addition of monomeric unit, and two protons are released thereby.Oxidation of aniline in acid medium gives regular polymer chains containing more than 95% of parasubstituted units connected in a head-to-tail mode [3]. Regular structure determines polyconjugation and a unique set of properties intrinsic to polyaniline, in particular high electronic and proton conductivity, redox power, and paramagnetism [1]. Unlike other kinds of chain polymerization, e.g., radical polymerization where oxidant participates only in chain initiation, oxidative polymerization requires a large amount of oxidant [4] which is consumed for each act of addition of monomer unit. Therefore, molar concentration of oxidant should be comparable with the monomer concentration. Here, oxidant operates throughout the entire process until addition of the last monomer portion to polymer chain.Polymerization of aniline can be performed by electrochemical or chemical methods with the use of various oxidants. In ...

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Section: Polymerization Initiation Centermentioning

confidence: 92%

Oxidation of aniline with strong and weak oxidants

Sapurina

Stejskal

2012

Russ J Gen Chem

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“…One may note that for polymer films where the amount of solvent inside the deposited film is determined by its presence inside solvation shells of incorporated ions one should expect that the egress of these ions from the film should be accompanied by a parallel removal of this solvent; i.e., the value of x in Eqs. (9) and (15) is to be positive and expectedly close to the value of n AN : x ≈ n AN . As it is discussed below, the experimental value of x is negative.…”

Section: Methodology For Determination Of Parameters Of Electropolymementioning

confidence: 75%

“…Use of Eqs. (8) and (9) gives an expression for the ratio of the changes of the film mass and of its redox charge in the course of the film discharge ( Fig. 5) so that the value of x may be found from its slope:…”

Section: Methodology For Determination Of Parameters Of Electropolymementioning

confidence: 99%

“…Important information on such electroactive polymers and polymer-containing composites is provided by the technique of electrochemical quartz crystal microbalance (EQCM) which may be applied under in situ electrochemical conditions. This method has been used for studies of the film deposition and discharge processes of such polymers as polypyrrole [1][2][3][4][5][6], polythiophene [7], polyaniline [8], in particular the one synthesized under conditions of the cathodic oxygen reduction [9], poly(o-methoxyaniline) [10], poly(o-toluidine) [11], polyparaphenylene [12], 3,4-polyethylenedioxythiophene [13][14][15][16], and poly-3-octylthiophene [17] as well as metal-or metal-oxide-based polymeric nanocomposites [18][19][20][21][22][23][24]. The technique has also been employed for studies of adsorption and desorption process for various gases and ions on electrode surfaces [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical quartz crystal microbalance study of magnesium porphine electropolymerization process

Istakova

Конев

Goncharova

et al. 2020

J Solid State Electrochem

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Material and charge balances in the course of the electropolymerization process of the non-substituted Mg(II) porphine (MgP) at a low oxidation potential from its acetonitrile solutions of various concentrations have been studied via the in situ electrochemical quartz crystal microbalance method (EQCM). Thus, registered electrode mass increase due to the MgP oxidation at its surface has been used, in combination with in situ spectroelectrochemical data, for determination of the key parameters of the polymerization process and of the magnesium polyporphine films deposited on the electrode surface: current efficiency of the film deposition process, average charge spent for transformation of a monomer molecule into monomer unit inside the film, number of monomer units inside the deposited film, average number of valence bonds per one monomer unit inside the film. Besides, the EQCM method applied to the discharge process of the electropolymerized film has allowed us to estimate the average charging (oxidation) degree of the monomer unit inside the film at the polymerization potential and the degree of the solvent participation in the course of the polymer's redox transitions. It has been established that the number of bonds between porphine units is within the range of 2.2 to 2.4, with its slight increase for films deposited at higher monomer concentrations. Conclusions on the structure of polyporphine chains have been made.

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