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Gizdavic-Nikolaidis M.R.,University of Auckland | Easteal A.J.,University of Auckland | Zujovic Z.D.,University of Auckland | Zujovic Z.D.,Serbian Institute of General and Physical Chemistry
Journal of Physical Chemistry C

Facile and fast microwave- (MW) assisted synthesis of copolymers of aniline and 2-aminobenzoic acid (2ABA) or 2-aminosulfonic acid (2SULFO) was performed by chemical polymerization of several mole ratios of aniline to functionalized aniline (FA). The physicochemical properties of the copolymers thus prepared were compared with the poly(aniline-co-2-aminobenzoic acid) (2ABAPANI) and poly(aniline-co-2-sulfonic acid) (2SULFOPANI) copolymers synthesized by conventional synthesis (CS) at the same temperature. FTIR and UV-vis spectra show the 2ABAPANI or 2SULFOPANI structure in all samples synthesized either conventionally or in the microwave reactor, however the yield was 2.5-3 times higher for nanostructured functionalized copolymers (fPANI) synthesized by MW. The effect of microwave irradiation on the antioxidant properties of the nanostructured 2ABAPANI and 2SULFOPANI copolymers was investigated. These samples showed 2.1-2.4 times better radical scavenger efficacy than their conventionally synthesized counterparts. A formation mechanism of polyaniline nanofibers under MW conditions is tentatively proposed based on thermal and nonpurely thermal effects on the nucleation modes. © 2010 American Chemical Society. Source

Gavrilov N.,University of Belgrade | Dasic-Tomic M.,Serbian Institute of General and Physical Chemistry | Pasti I.,University of Belgrade | Ciric-Marjanovic G.,University of Belgrade | And 2 more authors.
Materials Letters

Nitrogen-containing carbonized polyaniline nanotubes/nanosheets were used to synthesize a novel type of supported Pt nanoparticles electrocatalyst PtNPs/Carb-nanoPANI, with the Pt nanoparticles of ∼ 9 nm in diameter. PtNPs/Carb-nanoPANI nanocomposite was characterized by transmission electron microscopy, cyclovoltammetry, thermogravimetric and XRD analyses. Its electrocatalytic activity towards the oxygen reduction reaction in both the alkaline and acidic solutions was studied by a rotating disc technique. In acidic media, this electrocatalyst was compared to both smooth platinum and commercial C-supported Pt-based electrocatalyst. Its higher specific electrocatalytic activity, which amounted to ∼ 1 mA cm- 2 in the region of diffusion control, was proved. High electrocatalytic activity of PtNPs/Carb-nanoPANI towards the ethanol oxidation reaction in acidic medium was also evidenced. © 2010 Elsevier B.V. All rights reserved. Source

Gizdavic-Nikolaidis M.R.,University of Auckland | Jevremovic M.,Public Company Nuclear Facilities of Serbia | Zujovic Z.D.,University of Auckland | Zujovic Z.D.,Serbian Institute of General and Physical Chemistry
Journal of Physical Chemistry C

A series of energy- and time-efficient enhanced microwave syntheses (EMS) of polyaniline (PANI) have been performed and are discussed herein. The syntheses were performed at different microwave power levels while keeping the reaction system at a constant temperature of 24 ± 1 °C, with the samples extracted after 10 min of reaction. Molecular weights were determined with GPC (gel permeation chromatography) and showed that the molecular weight of the microwave-generated materials depends on applied power: the higher the power level, the greater the molecular weight. The chemical structure was investigated by FTIR and UV-vis spectroscopy, while the morphology was imaged using scanning electron microscopy (SEM). FTIR and UV-vis spectroscopy confirmed the formation of PANI, and SEM indicated the presence of a mixed morphology, with a prevalence of nanofibers with different aspect ratios. The conductivity of the samples (ca. 3-3.5 S cm -1) was found to be relatively independent of microwave power levels. Surface area measurements were carried out using Brunauer-Emmett-Teller (BET) method, with samples synthesized using EMS showing higher surface areas when compared with conventionally synthesized PANI. The fact that molecular weight depends on applied power implies that microwave-enhanced synthesis can be used to fine-tune PANI reaction conditions, directing it toward specific properties. © 2012 American Chemical Society. Source

Gizdavic-Nikolaidis M.R.,University of Auckland | Easteal A.J.,University of Auckland | Zujovic Z.D.,University of Auckland | Zujovic Z.D.,Serbian Institute of General and Physical Chemistry
Macromolecular Rapid Communications

We present the first fast and facile microwave assisted synthesis of polyaniline (PANI) nanofibers ("MWA synthesis"). Under conventional synthesis (CS), the polymer was produced with 79.7% yield after 5 h at ambient temperature. However, under microwave irradiation, the nanofibers were produced with yield of 76.2% after only 5 mm, i.e., with 78.8% after 20 min at ambient temperature. The FTIR and Raman spectra show the PANI structure in all samples either synthesized conventionally or in the microwave. SEM and TEM confirm the nanofibrillar morphology. (Figure Presented) © 2010 WILEY-VCH Verlag GmbH & Co. KGaA. Source

Bascarevic Z.,University of Belgrade | Komljenovic M.,University of Belgrade | Miladinovic Z.,Serbian Institute of General and Physical Chemistry | Nikolic V.,University of Belgrade | And 3 more authors.
Construction and Building Materials

The geopolymers based on fly ash were exposed to the concentrated (6 M) NH4NO3 solution for 540 days. The highest compressive strength decrease occurred in the initial 28 days testing period. Study of the effects of the NH4NO3 solution on the geopolymer structure indicated leaching of alkali and alkaline earth cations and breaking of -Si-O-Al- bonds in aluminosilicate gel. The reduction of compressive strength of the geopolymers was associated with the structural defects in the aluminosilicate gel created by breaking of -Si-O-Al- bonds. Subsequent fluctuation in compressive strength was a result of the structural defects reparation by silicon.© 2013 Elsevier Ltd. All rights reserved. Source

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