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Stara Pazova, Serbia

Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | Bober P.,Czech Institute of Macromolecular Chemical | Rozlivkova Z.,Czech Institute of Macromolecular Chemical | And 3 more authors.
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2011

The oxidative polymerization of p-phenylenediamine with silver nitrate by using various oxidant/monomer mole ratios in aqueous solutions of both acetic and nitric acid was studied experimentally and computationally. The produced micro/nanostructured conducting poly(p-phenylenediamine)-silver composites, reaching the conductivities >104 S/cm, were characterized by conductivity and density measurements, gel permeation chromatography, transmission electron microscopy, UV-visible, FTIR, and Raman spectroscopies. The highest conductivity was 31,700 S/cm for poly(p-phenylenediamine) base-silver (81.4 wt % Ag). The unexpected increase of conductivity after deprotonation of polymer component is discussed on the basis of interfacial electrical barriers and their removal. Theoretical study of the mechanism of p-phenylenediamine oxidation has been based on the AM1 semi-empirical quantum chemical computations of the heat of formation of the reaction intermediates, taking into account the influence of pH and solvation effects. Quantum chemical predictions of molecular structure of poly(p-phenylenediamine) were correlated with spectroscopic findings. © 2011 Wiley Periodicals, Inc. Source


Janosevic A.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Sljukic Paunkovic B.,University of Belgrade | Pasti I.,University of Belgrade | And 3 more authors.
Synthetic Metals | Year: 2012

The oxidation of aniline with ammonium peroxydisulfate (APS) in aqueous solution of the plant-derived polyphenol, tannic acid, is reported. The effect of initial mole ratios [tannic acid]/[aniline] and [APS]/[aniline] on molecular structure, morphology, conductivity, and electroactivity of synthesized materials (PANI-TA) was investigated by UV-Vis, FTIR, Raman and EPR spectroscopies, scanning and transmission electron microscopies (SEM and TEM), conductivity measurements, and cyclic voltammetry, respectively. PANI-TA nanorods with the average diameter of 70-100 nm and conductivity of 1 × 10-3 S cm-1 were synthesized at [tannic acid]/[aniline] = 0.01 and [APS]/[aniline] = 1, while nonconductive, solid microspheres were obtained at [tannic acid]/[aniline] = 0.1 and [APS]/[aniline] = 2. The mechanism of the early stages of simultaneous oxidation of aniline and tannic acid has been computationally studied by the RM1/COSMO method. © 2012 Elsevier B.V. All rights reserved. Source


Marjanovic B.,Centrohem | Juranic I.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade
Journal of Physical Chemistry A | Year: 2011

New computational insights into the mechanism of the Boyland-Sims oxidation of arylamines with peroxydisulfate (S 2O 8 2?) in an alkaline aqueous solution are presented. The key role of arylnitrenium cations, in the case of primary and secondary arylamines, and arylamine dications and immonium cations, in the case of tertiary arylamines, in the formation of corresponding o-aminoaryl sulfates, as prevalent soluble products, and oligoarylamines, as prevalent insoluble products, is proposed on the basis of the AM1 and RM1 computational study of the Boyland?Sims oxidation of aniline, ring-substituted (2-methylaniline, 3-methylaniline, 4-methylaniline, 2,6-dimethylaniline, anthranilic acid, 4-aminobenzoic acid, sulfanilic acid, sulfanilamide, 4-phenylaniline, 4-bromoaniline, 3-chloroaniline, and 2-nitroaniline) and N-substituted anilines (N-methylaniline, diphenylamine, and N,N-dimethylaniline). Arylnitrenium cations and sulfate anions (SO 4 2?) are generated by rate-determining two-electron oxidation of primary and secondary arylamines with S 2O 8 2?, while arylamine dications/immonium cations and SO 4 2? are initially formed by two-electron oxidation of tertiary arylamines with S 2O 8 2?. The subsequent regioselectivity-determining reaction of arylnitrenium cations/arylamine dications/immonium cations and SO 4 2?, within the solvent cage, is computationally found to lead to the prevalent formation of o-aminoaryl sulfates. The formation of insoluble precipitates during the Boyland?Sims oxidation of arylamines was also computationally studied. © 2011 American Chemical Society. Source


Janosevic A.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | Trchova M.,Czech Institute of Macromolecular Chemical | Stejskal J.,Czech Institute of Macromolecular Chemical
Materials Letters | Year: 2010

Self-assembled polyaniline nanorods were synthesized by the oxidation of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 3,5-dinitrosalicylic acid, using the template-free falling-pH method. The effects of the mole ratio of 3,5-dinitrosalicylic acid to aniline, i.e., of starting pH, monomer concentration, and reaction time on the yield of polymerization, molecular-weight distribution, molecular structure, morphology, and conductivity of the prepared polyanilines have been studied by gel-permeation chromatography, elemental analysis, FTIR and Raman spectroscopies, scanning and transmission electron microscopies, and conductivity measurements. The weight-average molecular weights and polydispersity index were in the range 36,400-54,900 and 3.7-7.6, respectively. Synthesized polyaniline nanorods have a diameter of 25-280 nm and a length of 0.2-1.3 μm, and conductivities in the range (1.2-4.6) × 10-2 S cm-1. The formation mechanism of self-assembled polyaniline nanorods has been discussed. © 2010 Elsevier B.V. Source


Stevic M.C.,University of Belgrade | Ignjatovic L.M.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | Marjanovic B.,Centrohem | And 2 more authors.
Journal of Electroanalytical Chemistry | Year: 2012

Experimental study of the electro-oxidation behavior of 6-hydroxyquinoline (6HQ) has been performed using cyclic voltammetry (CV) on a glassy carbon paste electrode (GCPE). The theoretical study of the 6HQ electrochemical oxidation mechanism, based on the AM1 semi-empirical quantum chemical computations of the heats of formation and ionization energy of reaction intermediates, taking into account influence of pH and solvation effects, has also been conducted. It was established that a two-electron, irreversible process, controlled by diffusion of electroactive species, is responsible for an oxidation peak of 6HQ that appears in all cyclic voltammograms recorded on a clean electrode, in solutions of pH range 2-12, with a supporting electrolyte of Britton-Robinson buffer/methanol. A single-electron oxidation of 6HQ leads, depending on pH, to the formation of various free radical species that combine to make C5-C5 coupled 6HQ dimers which, after being oxidized once more, give quinonoid-type compounds. The irreversible electrochemical oxidation of 6HQ does not stop after the dimerization step but proceeds further to the formation of oligo/poly(6HQ). The optimum conditions for Differential Pulse Voltammetry (DPV) determinations were established and it was shown that for more sensitive quantitative determinations Adsorptive Stripping Differential Pulse Voltammetry (AdSDPV) can be used. © 2012 Elsevier B.V. All rights reserved. Source

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