Progress in conducting/semiconducting and redox-active oligomers and polymers of arylamines

Recent advances in synthesis, characterization and application of the selected conducting/semiconducting and redox-active oligomers and polymers of arylamines are reviewed. A brief historical background of the selected topics is given. The overview of the preparation, structure and properties of polyaniline, substituted polyanilines, especially those obtained by the oxidative polymerization of p-substituted anilines, poly(1-aminonaphthalene) and its derivatives, carbocyclic and heterocyclic polyaryldiamines such as poly(p-phenylenediamine) and polydiaminoacridines, is presented. The mechanism of formation of polyaniline nanostructures is discussed. Recent approaches to the preparation of one-dimensional polyaniline nanostructures are concisely reviewed, with special attention paid to the template-free falling-pH method. Current and potential future applications of oligo/polyarylamines are briefly discussed. [Projekat Ministarstva nauke Republike Srbije, br. OI 172043

Oksidativna polimerizacija anilina u prisustvu fenolnih kiselina

Aniline was oxidized with ammonium peroxydisulfate (APS) in aqueous solutions of various phenolic acids: 5-sulfosalicylic acid (SSA), 3,5-dinitrosalicylic acid (DNSA) and gallic acid (GA). Polymerizations were performed at the constant molar ratios [acid]/[aniline] = 0.5 and [APS]/ /[aniline] = 1.25. The conductivity of synthesized polyaniline (PANI) is affected by the dopant anion type and decreases in order: PANI-SSA > > PANI-DNSA > PANI-GA, the last polymer being nonconducting. This decrease is in accordance with the increase of initial pH value of the reaction mixture. The differences in molecular structure of synthesized PANI have been revealed by FTIR spectroscopy. FTIR spectra of PANI-SSA and PANI-DNSA show typical features of PANI conductive emeraldine salt segments. On the contrary, FTIR spectrum of PANI-GA shows absence of bands typical for conducting PANI polaronic lattice, and indicates the higher oxidation state of this polymer than that of emeraldine, the presence of substituted phenazines as constitutional units, as well as significant content of monosubstituted benzene rings which reflects low polymerization degree and/or pronounced chain branching. The strong hydrogen bonding between GA and PANI can obstruct propagation of oligoanilines and formation of longer conducting PANI chains.Polianilin (PANI) sintetisan je oksidacijom anilina u vodenim rastvorima fenolnih kiselina: 5-sulfosalicilne (SSA), 3,5-dinitrosalicilne (DNSA) i galne kiseline (GA), koristeći amonijum-peroksidisulfat (APS) kao oksidaciono sredstvo. Sinteze su urađene pri konstantnim polaznim molskim odnosima kiselina/anilin i APS/anilin. Utvrđeno je da sa porastom jačine fenolne kiseline raste električna provodljivost dobijenih polianilina. PANI-GA je neprovodan, PANI-DNSA pokazuje provodljivost ~10-3 S cm-1, dok je provodljivost PANI-SSA ~10-1 S cm-1. Na osnovu uporedne analize FTIR spektara protonovanih i deprotonovanih formi ovih polimera diskutovane su razlike u njihovoj molekulskoj strukturi

Sinteza nanostrukturiranog provodnog polianilina u prisustvu 5-sulfosalicilne kiseline

Oxidative polymerizations of aniline with ammonium peroxydisulfate in aqueous solution of 5-sulfosalicylic acid (SSA), were performed at the constant molar ratio [oxidant]/[monomer] = 1.25, by using various initial molar ratios of SSA to aniline. It was shown that the ratio [SSA]/[aniline] has a crucial influence on the molecular structure, morphology, and conductivity of synthesized polyaniline5-sulfosalicylate (PANI-SSA), as well as on the yield and temperature profile i.e. the mechanism of polymerization process. The yield of PANI-SSA was 80 - 86% for [SSA]/[aniline] ratios in the range 0.25-1.0. Granular PANI-SSA was obtained by the oxidative polymerization of in situ formed anilinium 5-sulfosalicylate ([SSA]/[aniline] = 1.0). The initial induction period was followed by the rapid exothermic polymerization of aniline during the oxidation of anilinium 5-sulfosalicylate with peroxydisulfate. Nanostructured PANI-SSA was synthesized by the oxidation of the mixture of dianilinium 5-sulfosalicylate and aniline ([SSA]/[aniline] = 0.25), which proceeds in two exothermic phases well separated with an athermal period. The presence of nanocylinders (nanorods, possibly nanotubes), with the average diameter of 95-250 nm and the length of 0.5-1.0 μm has been revealed by scanning electron microscopy. It was concluded that PANI nanocylinders are formed when reaction solution has the initial pH > 3.5. Electroconductivity of synthesized polyanilines was in the range 0.01-0.17 S cm-1, and it increases with increasing molar ratio of SSA to aniline. Molecular structure of synthesized polyanilines was investigated by FTIR spectroscopy. Besides the characteristic bands of standard PANI in emeraldine form (benzenoid, quinonoid, and semiquinonoid units), the band attributable to substituted phenazine structural units was observed at -1415 cm-1 in the FTIR spectrum of nanostructured PANI-SSA sample.Elektroprovodni nanostrukturirani polianilin sintetisan je oksidacijom, anilina u vodenom rastvoru 5-sulfosalicilne kiseline, koristeći amonijum peroksidisulfat kao oksidaciono sredstvo. Utvrđeno je da početni molski odnos 5-sulfosalicilne kiseline i anilina ima odlučujući uticaj na temperaturni profil i prinos reakcije polimerizacije, kao i na molekulsku strukturu, morfologiju i elektroprovodljivost dobijenog polianilina. Prisustvo nanoštapića prosečnog prečnika 95-250 nm i dužine 0,5-1,0 μm utvrđeno je skenirajućom elektronskom mikroskopijom. Gelpropusnom hromatografijom određene su vrednosti molame mase usrednjene po masi i indeksa polidisperznosti. Elektroprovodljivost sintetisanih uzoraka polianilina je 0,01-0,17 S cm-1. FTIR spektroskopijom ispitana je molekulska struktura sintetisanih polianilina

Nanostructured materials for sensing Pb(II) and Cd(II) ions: Manganese oxohydroxide versus carbonized polyanilines?

Nanostructured materials including three different carbonized polyanilines and manganese oxyhydroxide were prepared and evaluated as electrode materials for sensing of lead and cadmium ions in aqueous media. Anodic stripping voltammetry results indicated that all prepared materials could be successfully used for determination of these two heavy metal ions. Carbonized polyaniline-based electrodes have higher signal and lower limits of detection (10-7 М) compared to manganese oxyhydroxide-based electrode. Among the three studied carbonized polyanilines, the one that was derived from polyaniline precursor produced in the presence of 3,5-dinitrosalicyclic acid showed the highest electrocatalytic activity towards the lead and cadmium oxidation. [Projekat Ministarstva nauke Republike Srbije, br. OI172043 i br. III45014

Electrochemical Sensing of Cadmium and Lead Ions in Water by MOF-5/PANI Composites

For the first time, composites of metal-organic framework MOF-5 and conjugated polymer polyaniline (PANI), (MOF-5/PANI), prepared using PANI in its conducting (emeraldine salt, ES) or nonconducting form (emeraldine base, EB) at various MOF-5 and PANI mass ratios, were evaluated as electrode materials for the electrochemical detection of cadmium (Cd2+) and lead (Pb2+) ions in aqueous solutions. Testing of individual components of composites, PANI-ES, PANI-EB, and MOF-5, was also performed for comparison. Materials are characterized by Raman spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS), and their electrochemical behavior was discussed in terms of their zeta potential, structural, morphology, and textural properties. All examined composites showed high electrocatalytic activity for the oxidation of Cd and Pb to Cd2+ and Pb2+, respectively. The MOF/EB-1 composite (71.0 wt.% MOF-5) gave the highest oxidation currents during both individual and simultaneous detection of two heavy metal ions. Current densities recorded with MOF/EB-1 were also higher than those of its individual components, reflecting the synergistic effect where MOF-5 offers high surface area for two heavy metals adsorption and PANI offers a network for electron transfer during metals’ subsequent oxidation. Limits of detection using MOF/EB-1 electrode for Cd2+ and Pb2+ sensing were found to be as low as 0.077 ppm and 0.033 ppm, respectively. Moreover, the well-defined and intense peaks of Cd oxidation to Cd2+ and somewhat lower peaks of Pb oxidation to Pb2+ were observed at voltammograms obtained for the Danube River as a real sample with no pretreatment, which implies that herein tested MOF-5/PANI electrodes could be used as electrochemical sensors for the detection of heavy metal ions in the real water samples

Synthesis and characterization of conducting polyaniline nanotubes in the presence of colloidal TiO2 nanoparticles

Conducting polyaniline nanotubes were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in water, in the presence of colloidal TiO2 nanoparticles of an average diameter ~5 nm. Polyaniline-TiO2 nanocomposite has been characterized by the electrical conductivity measurements, thermogravimetric analysis, FTIR spectroscopy, scanning and transmission electron microscopies. The electrical conductivity of synthesized nanocomposite was 1.1 × 10–3 S cm–1, slightly higher than that of pure polyaniline prepared under the same conditions. Polyaniline nanotubes have an outer diameter of 45–230 nm nm, an inner diameter of 15–130 nm, and a length extending from 0.5 to 2.0 μm.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Struktura i stereohemija poli-(1-naftilamina) elektrohemijski sintetisanog u neutralnom acetonitrilnom rastvoru

Poly-(1-naphthylamine) films were synthesized potentiodinamically and potentiostatically from 1-naphthylamine in neutral acetonitrile medium using a platinum electrode. These polymer films were investigated by infrared spectroscopy. Contrary to earlier published results neglecting the stereochemistry of the poly-(1-naphthylamine), we predict on the basis of quantum stereochemical analysis of the possible structural subunits of the polymer, that the ordinary N–C(4) coupled product is not predominant in the polymer because it is far removed from the expected planarity. Based on the results of IR investigations and semiempirical quantum chemical calculations, it is proposed that the polymer products are formed via mixed N–C(4), N–C(5) and N–C(7) coupling routes. The heats of formation of the oxidized 1-naphthylamine dimers and hexamers were calculated.Poli-(1-naftilaminski) filmovi sintetisani su potenciostatski i potenciodinamički iz neutralnog acetonitrilnog rastvora 1-naftilamina na platinskoj elektrodi. Ovi polimerni filmovi ispitivani su IR spektroskopijom. Za razliku od ranije publikovanih rezultata koji su zanemarivali stereohemiju poli-1(-naftilamina), u ovom radu se predviđa na osnovu kvantne stereohemijske analize mogućih strukturnih jedinica polimera da uobičajeni N–C(4) kuplovani produkt nije predominantan u polimeru, jer njegova struktura nije planarna. Na osnovu rezultata IR ispitivanja i semiempirijskih kvantno-hemijskih proračuna mi pretpostavljeno je da se polimerni produkti formiraju kombinovanim N–C(4), N–C(5) i N–C(7) načinima vezivanja 1-naftilamina. U ovom radu su takođe izračunate toplote nastajanja oksidovanih dimera i heksamera 1-naftilamina

Hibridni funkcionalni Pani/TiO2 nanokompoziti za tretman degradacije organskih boja

A calling need for environmental protection is not abating and high demands have been set for the current topic that deals with applied technologies for removal of organic pollutants. The AOPs appear to be one of the most effective processes, where heterogeneous photocatalysis using efficient UV light-harvesting TiO2nanocrystals has unquestionably become one of the most com-monly used process for dyes degradation treatment. Limited photocatalytic efficiency of TiO2under sunlight illumination was overcame bycoupling with polyaniline (PANI) as notably investigated conductive polymer. Reducing the level of e-/h+recombination in TiO2and photosensitized proper-ties of PANI was the basis for creation of new functional PANI/TiO2nanocomposites. Such hybrid functional nanomaterials consisting of conductive polymers and dissimilar nanocrystals manifest the unique properties, usually not characteristic of independent componentsbut their synergistic effect. Series of developed functional nanocomposites based on PANI and colloidal TiO2nanoparti-cles (NPs) (TP), carbonized PANI and colloidal TiO2NPs (TPC) and carbonized PANI and TiO2nanotubes (NTs) (TTPC) by the efficient and harmless synthesis pathways are presented. Differently shaped TiO2nanocrystals are carefully prepared via sol-gel and hydrothermal synthesis and the influence of their size and shape on the photocatalytic efficiency of hybrid nanocomposites was evaluated. The non-carbonized PANI/TiO2nanocomposites were synthesized by the chemical oxida-tive polymerization of aniline with ammonium peroxydisulfate, in the presence of selected TiO2nanocrystals, while the carbonized class was obtained in the subsequent carbonization process, following the polymerization, in an inert atmosphere at 650 °C. The morphology and structureof these nano-based photocatalysts was determined by TEM analysis and Raman spectroscopy. Func-tionality of nanocomposites was evaluated following the photocatalytic degradation processes of model compoundsMethylene blue and Rhodamine B and enhanced degradation efficiencies in the used dyes were observedAktuelna potreba za zaštitom životne sredine ne jenjava i s tim u vezi postavljeni su visoki zahtevi vezani za tematiku primenjenih tehnologija za uklanjanje organskih zagađujućih supstanci. Ispostavlja se da napredni procesi oksidacije (engl. Advanced oxidation processes, AOPs) predstavljaju jedan od najefikasnijih procesa, među kojima heterogena fotokataliza, bazirana na upotrebi nanokristala TiO2 aktiviranih UV zračenjem, nesumnjivo predstavlja jedan od najčešće korišćenih tretmana za degradaciju organskih boja. Problem ograničene fotokatalitičke efikasnosti TiO2 pod dejstvom sunčevog zračenja može se prevazići formiranjem kompozita sa polianilinom (PANI), čija se uloga bazira na smanjenju rekombinativnih procesa e-/h+, kao i sposobnosti PANI-a da optički aktivira nanokristale TiO2, što je bila osnova za formiranje novih funkcionalnih PANI/TiO2 nanokompozita. Takvi hibridni nanomaterijali bazirani na provodnom polimeru i nanokristalima različitih oblika pokazuju jedinstvena svojstva koja najčešće nisu karakteristika pojedinačnih komponenti, već njihovog sinergističkog dejstva. Efikasnim i ekološki prihvatljivim sintezama razvijena je serija funkcionalnih nanokompozita na bazi PANI-a i koloidnih TiO2 nanočestica (NPs) (TP), karbonizovanog PANI-a i koloidnih TiO2 NPs (TPC) i karbonizovanog PANI-a i TiO2 nanotuba (NTs) (TTPC). Nanokristali TiO2 različitog oblika pažljivo su sintetisani sol-gel i hidrotermalnom metodom i procenjen je uticaj njihove veličine i oblika na fotokatalitičku efikasnost hibridnih nanokompozita. Nekarbonizovani PANI/TiO2 nanokompoziti sintetisani su hemijskom oksidativnom polimerizacijom anilina sa amonijum peroksidisulfatom, u prisustvu odabranih nanokristala TiO2, dok je karbonizovana serija uzoraka dobijena naknadnim procesom karbonizacije, prateći polimerizaciju, u inertnoj atmosferi na 650 °C. Morfologija i struktura sintetisanih fotokatalitički aktivnih sistema ispitana je TEM analizom i Ramanskom spektroskopijom. Funkcionalnost nanokompozita je procenjena prateći procese fotokatalitičke degradacije model-jedinjenja Methylene blue i Rhodamine B i primećena je povećana efikasnost degradacije testiranih organskih boja36. Međunarodni kongres o procesnoj industriji - PROCESING ′23 : zbornik radova ; 1-2. jun, Šaba

Ferromagnetic response of nanocomposites based on polyaniline and TiO2 nanocrystals of different shape

Ferromagnetic polyaniline (PANI)/TiO2 nanocomposites were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate (APS), in the presence of colloidal TiO2 nanoparticles and TiO2 nanotubes, without added acid. The morphological, magnetic and structural properties of the PANI/TiO2 nanocomposites were studied by SEM microscopy, SQUID magnetometer and FTIR spectroscopy. The electrical conductivity of synthesized nanocomposites was ~10-3 Scm-1. The room temperature ferromagnetic response significantly depends on shape of TiO2 nanoparticles