Oxidative Polymerization Of Aniline Research Articles

Influence of monomer content on course of aniline polymerization in presence of high surface area carbon

A series of carbon/polyaniline (C/Pani) composites were synthesized by oxidative polymerization of aniline in the presence of carbon in acid media. Biomass-derived activated carbon (AC) having 1740m2/g surface area was used as the carbon component. The aniline loadings varied from 8 to 60wt%. A composition of the composites was determined by CHNS analysis. Porous structure of polyaniline, carbon and C/Pani composites was characterized with nitrogen adsorption at 77K. Structure of the composites, polyaniline and carbon was studied by Fourier transform infrared spectroscopy (FTIR). Electrochemical properties of the samples were investigated by cyclic voltammetry technique in 1M H2SO4 at 25°C. It has been shown that the aniline loading and presence of the carbon in the reaction mixture determine final product of the polymerization. At the aniline loading <30wt%, 4-aminodiphenilamine (4-ADPA) and phenazine-ring containing structures (PhzR) being intermediates in the aniline polymerization are predominantly formed and registered by electrochemical methods. Polyaniline formation is observed for the samples with aniline loading >40wt%.

Enhanced degradation of BPA in water by PANI supported Ag/TiO2 nanocomposite under UV and visible light

PANI supported Ag@TiO2 nanocomposite was synthesized via oxidative polymerization of aniline on Ag@TiO2. The Ag@TiO2 nanocomposite was synthesized by the photo reduction of Ag nanoparticles on hydrothermally synthesized TiO2 nanofibers. Raman analysis revealed that the anatase phase of TiO2 was synthesized showing typical peaks at 195 cm−1, 396 cm−1, 514 cm−1, and 637 cm−1. The incorporation of PANI, a carbonaceous material was confirmed by appearance of D-band and G-band in Ag@TiO2-PANI that were located at 1505 cm-1 and 1603 cm−1 respectively. X-ray diffraction (XRD) analysis confirmed the anatase phase of TiO2 was synthesized. Transmission electron microscopy analysis (TEM) analysis revealed that TiO2 nanofibers were synthesized successfully and Ag nanoparticles of different sizes were deposited on their surface. X-ray Photon Spectroscopy (XPS) survey scan of the Ag@TiO2-PANI-nanocomposite revealed that the nanocomposite was made from C, O, Ag, Ti, and N. DRS and Tauc`s plot estimated the band gap of Ag@TiO2-PANI to be 3.0 eV A comparative study of the photocatalytic performance of Ag@TiO2-PANI catalyst showed better degradation performance under both conditions than pristine TiO2, and Ag@TiO2 with a degradation of up to 99.7% under visible light irradiation. The degradation experiments showed that the reactive species that were dominant in the degradation of BPA were h+ and O2-. Ag@TiO2-PANI nanocomposite was re-used to degrade BPA for up to four cycles without losing much of its photocatalytic ability with a removal of at least 90% in the fourth cycle.

One-pot facile simultaneous in situ synthesis of conductive Ag-polyaniline composites using Keggin and Preyssler-type phosphotungstates.

Two heteropolytungstate structures, Keggin (H3PW12O40) and Preyssler (H14[NaP5W30O110]), were used to synthesize conductive silver nanoparticle–polyaniline–heteropolytungstate (AgNPs–PAni–HPW) nanocomposites. During the oxidative polymerization of aniline, heteropolyblue was generated and served as the reducing agent to stabilize and distribute AgNPs within “PAni–Keggin” and “PAni–Preyssler” matrixes as well as on their surfaces. The prepared nanocomposites and AgNPs were characterized using UV-visible (UV-Vis) and Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), pore size distribution BET, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). UV-Vis results showed different stages of the formation of metal NPs embedded in the polymer–HPW composites, and FT-IR spectra presented characteristic bands of PAni, Keggin and Preyssler anions in the composites confirming no changes in their structures. The presence of AgNPs and an intensely crystalline matrix were confirmed by the XRD pattern. The BET surface areas were found to be 38.426 m2 g−1 for “AgNPs–PAni–Keggin” and 29.977 m2 g−1 for “AgNPs–PAni–Preyssler” nanocomposites with broad distributions of meso-porous structure for both nanocomposites. TEM and SEM images confirmed that the type of heteropolyacids affected the size of AgNPs. This is the first report that uses Keggin and Preyssler-type heteropolytungstate to synthesize “AgNPs–PAni–HPW” nanocomposites in an ambient condition through a low-cost, facile, one-pot, environmentally friendly and simultaneous in situ oxidative polymerization protocol.

Laccase-Catalyzed Aniline Polymerization on Multiwalled Carbon Nanotubes: the Effect of Surface Carboxyl Groups on Polyaniline Properties

Polyaniline/carboxylated multiwalled carbon-nanotube composites were synthesized with the use of laccase from the fungus Trametes hirsuta as a catalyst of aniline oxidative polymerization. Atmospheric oxygen was an oxidant. Aniline dimer adsorbed on the carbon material surface served as an enhancer of the enzymatic polymerization of aniline. The composites were synthesized in deionized water without any acidic dopant. The structure, morphology, and electrochemical characteristics of the obtained nanocomposite were examined. It has been shown that the carboxylic groups on the surface of multiwalled carbon nanotubes result in the electrochemical activity of polyaniline in solutions with a neutral pH.

Modification of Nafion membrane by polyaniline providing uniform polymer distribution throughout the membrane

Oxidative polymerization of aniline in the presence of Nafion membranes has been carried out in a water–isopropanol mixture after preliminary impregnation of the membrane with the monomer (aniline) in aqueous isopropanol. Uniform distribution of polyaniline (PANI) throughout whole membrane volume has been found. On the contrary, aniline polymerization in water, even after preliminary impregnation of the membrane with the monomer, has resulted in the formation of PANI thin layer only on the membrane surfaces but not inside the membrane. The polymerization in water–isopropanol mixture has not led to the change in the membrane surface properties but has induced the structural reorganization of Nafion membrane accompanied by the increase in the membrane ionic cluster size and the distance between the fluorocarbon crystallites. Modification by PANI carried out either in water or in aqueous isopropanol solution has resulted in the decrease in the membrane proton conductivity by 5–10 times.

Electroconductive fibrous mat prepared by electrospinning of polyacrylamide-g-polyaniline copolymers as electrode material for supercapacitors

Fibrous mats were prepared by electrospinning of polyacrylamide-graft-polyaniline copolymers (PAAm-g-PANI) in a mixed solvent of water–dimethylformamide. The grafted copolymers were synthesized by oxidative polymerization of aniline in the presence of polyacrylamide; the effect of aniline/polyacrylamide ratio on the morphology of the fibrous mats and on their electrochemical properties was investigated. The composition and chemical structure of the copolymers were verified with FTIR. Polyaniline content higher than 40 wt% leads to the lack of electrospinability of the corresponding solutions. With polyaniline concentration increasing from 20 to 40 wt%, the fiber diameter decreases from 569 to 248 nm. WAXD study shows that the reflections from polyaniline crystallites are preserved during swelling, and the increasing polyaniline content results in the decreased sample compatibility with water. Galvanostatic charge–discharge, cyclic voltammetry by Trasatti method, and BET measurements reveal that most part of the charge in PAAm-g-PANI fibrous mats is stored via the pseudocapacitance mechanism. Maximum attained capacitances measured at 0.3 A g−1 were 102 F g−1 for the whole mass of electrode and 255 F g−1 for the mass of the active material.

High-performance supercapacitor coin cell: polyaniline and nitrogen, sulfur-doped activated carbon electrodes in aqueous electrolyte

We report herein a high energy density asymmetric supercapacitor cell consisting of polyaniline as a positive electrode and heteroatom-doped activated carbon as a negative electrode in aqueous sulfuric acid electrolyte. Polyaniline is prepared via oxidative polymerization of aniline using hydrothermally prepared manganese dioxide oxidant. Nitrogen and sulfur-doped activated carbon is prepared from AC by hydrothermal synthesis, employing ammonium thiocyanate as a heteroatom precursor. This asymmetric supercapacitor cell is cycled in the voltage range of 0 to 1.4 V, which exhibits an excellent performance with a high specific capacitance of 592 F g−1 and a high energy density of 80 W h kg−1 at a power density of 500 W kg−1, while symmetric cell configuration of individual components of polyaniline//polyaniline and activated carbon//activated carbon shows less performance, i.e., 35 W h kg−1 at 214 W kg−1 and 33 W h kg−1 at 286 W kg−1, respectively. Furthermore, asymmetric cells show good cycling stability retaining over 72% of its initial capacitance even after 10,000 continuous charge–discharge cycles at a higher discharge current, 5 mA. Practical device is demonstrated in the form of a CR2032 coin cell.

Synthesis of conductive polyaniline nanofibers in one step by protonic acid and iodine doping

In this study, protonic acid and iodine-doped conductive polyaniline (PANI) nanofibers were successfully fabricated in one step using ammonium persulfate (APS) and potassium biiodate (KH(IO3)2) as the co-oxidant. The resultant PANI nanofibers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and X-ray photoelectron spectroscopy. Their electrochemical properties were examined by cyclic voltammetry and the standard four-probe technique. Additionally, the molecular weight of the conductive PANI nanofibers was measured using a viscometer. It is found that the PANI nanofibers are codoped with protonic acid (hydrochloric acid and iodic acid) and iodine (I3 − and I5 −), and the KH(IO3)2 shows a significant acceleration effect for the oxidation polymerization of aniline. The conductivity of PANI reaches 21 S·cm−1, which is much higher than that of another PANI prepared by APS. This is ascribed to the iodine-doping effect and the nanofibers’ morphology. Additionally, the reaction mechanism of PANI is systematically discussed, and the codoped mechanism is proposed. Systematic investigations indicate that APS/KH(IO3)2 is an excellent co-oxidant for the preparation of highly conductive PANI nanofibers in one step.

Porous polylactic acid/carbon nanotubes/polyaniline composite film as flexible free-standing electrode for supercapacitors

Green polymer was used flexible substrate for sustainable energy storage in the present work. Namely, degradable and flexible free-standing composite film electrodes were designed with porous polymer-based nanocomposite films (polylactic acid (PLA)/carbon nanotubes (PLA/CNTs)) as conductive and degradable substrates for supercapacitors, via facile in-situ chemical oxidation polymerization of aniline with rapid-mixing chemical oxidation polymerization technique. The effect of the synthetic condition on the electrical conductivity and electrochemical properties of the resultant nanocomposite films was investigated. The porous polylactic acid/carbon nanotubes/polyaniline (P-PCP) sample P-PCP-3-H-2, which was prepared with an aniline concentration of 0.1 mol L−1 in presence of the porous polylactic acid/carbon nanotubes (P-PLA/CNTs) composite film after heat-treating at 60 °C for 1 h, possessed the best comprehensive performance, excellent mechanical strength with tensile strength of 18.7 MPa, highest specific capacitance of 510.3 F g−1 in 1.0 mol L−1 sulfuric acid electrolyte, good cycling stability of 111.5% after 2000 cycles and favorable flexible stability of 93.4% after 180º-bending for 700 cycles.

Development of Poly(aniline-co-o-toluidine)/TiO2 nanocomposite coatings for low carbon steel corrosion in 3.5% NaCl solution

Chemical oxidative polymerization of aniline (AN) and o-toluidine (OT) for the synthesis of copolymer, Poly(AN-co-OT) and its composite with TiO2 nanoparticles, Poly(AN-co-OT)/TiO2 employing ammonium persulfate as an oxidant and HCl as an external dopant were carried out. The homopolymers, Polyaniline and Poly(o-toluidine) were also prepared by following similar method. The synthesized polymers were characterized with FTIR spectroscopy, XRD/SEM/TEM analysis. The anticorrosive coatings were synthesized in dimethyl sulfoxide solution by dissolving synthesized polymers, and then were applied on low-carbon steel (LCS) samples using epoxy binder. The anticorrosive potential of the polymer coatings containing copolymer, copolymer-nanocomposite and homopolymers on LCS was evaluated in 3.5% NaCl at a temperature of 30 °C by open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. It was observed that the nanocomposite coating increases the protection efficacy by providing better barrier properties against corrosion as compared with neat copolymer and homopolymers coatings. The morphology of the coatings before and after 60 days LCS immersion in 3.5% NaCl solution was determined using SEM.

Two-step fabrication of iron-containing polyaniline composites for electrocatalytic hydrogenation of nitroarenes

Polyaniline + Fe + FeO + Fe3O4 composites were prepared as powder by a two-step process: (1) introduction of FeO into oxidative polymerization of aniline and (2) electrochemical reduction of the powder deposited on a Cu cathode in aqueous NaOH. The structure and morphological features were studied by atomic emission spectroscopy, X-ray diffraction analysis and electron microscopy. The polyaniline–iron composites were used in electrohydrogenation of p‑nitrobenzoic acid (p‑NBA). Their electrocatalytic activity in the process is due to the formation of iron particles as a result of the electrochemical reduction of Fe2+ cations in FeO. The electrocatalytic activity is clearly demonstrated by the electrocatalytic hydrogenolysis of the intermediate hydroxylaminobenzoate to the aminobenzoate. Magnetic properties have been determined for the composite with optimal FeO content before and after the electrocatalytic hydrogenation of p‑NBA.

Synthesis of conductive Cu-core / Ag-subshell / polyaniline-shell nanocomposites and their antimicrobial activity

Core shell technique was used to synthesize conductive Cu-core / Ag-subshell / polyaniline-shell nanocomposites (NCs) and evaluating their antimicrobial activities. This was achieved through two stages, firstly different Cu/Ag core shell nanoparticles (Cu/Ag NPs) were prepared (C/A1, C/A3, C/A5), using electroless plating technique by reduction of AgNO3 in alcoholic dispersion of Cu NPs at three different weight ratios of AgNO3: Cu. Secondly, the prepared Cu/Ag NPs were further coated with polyaniline (PANI) by oxidative polymerization of aniline in their aqueous dispersions to form PANI/(Cu/Ag) NCs (NC1, NC3, NC5). XRD patterns of Cu/Ag NPs revealed their bimetallic crystalline structure. SEM micrographs and EDAX data proved formation of Ag thin shell on the surface of Cu core. The concentration of this silvery layer increased from ≈ 38% (C/A1) to 68% (C/A5). SEM and EDAX data of NCs, showed that PANI film wrapped 60% to 63% of Cu/Ag NPs surface that Cu nearly diminished. The synthesized NCs possessed good electrical conductivity that increased with Ag content from 0.52 S/m (NC1) to13 (NC5) S/m. Good antimicrobial activities (antibacterial and antifungal), of Cu/Ag NPs and their NCs were obtained. Such good conductivity and antimicrobial activity nominate the NCs to be applied in electronic and biotechnical fields.

Facile immobilization of Pseudomonas fluorescens lipase on polyaniline nanofibers (PANFs-PFL): A route to develop robust nanobiocatalyst

Herein, we demonstrate the immobilization of Pseudomonas fluorescens lipase (PFL) on polyaniline nanofibers (PANFs) via physical adsorption. Polyaniline nanofibers (PANFs) were synthesized by the oxidative polymerization of aniline. The developed robust nanobiocatalyst (PANFs-PFL) exhibited eight times higher activity than free PFL. In addition, immobilization of lipase on PANFs imparted operational stability of the nanobioconjugate. The various reaction parameters for immobilization (viz. reaction time, pH, stirring rate and enzyme-support ratio) were optimized using statistical design in terms of lipase activity and loading. Furthermore, facile separation, enhanced reusability (upto 6 cycles) and thermostability (upto 75 °C) were additional advantages of the nanobioconjugate. The catalytic prowess of nanobioconjugate was examined in the kinetic resolution of (RS)-N-(4-(3-chloro-2-hydroxypropoxy)phenyl)acetamide and (RS)-1-(1-naphthyl) ethanol in comparison to free PFL. PANFs-PFL demonstrated 49.9% and 48.1% conversion for (RS)-N-(4-(3-chloro-2-hydroxypropoxy)phenyl)acetamide and (RS)-1-(1-naphthyl) ethanol, respectively which signified its importance as a nanobiocatalyst.

Preparation and Electrical Properties of Activated Carbon Grafted with Polyaniline Nanofiber

Activated carbon (AC) grafted with polyaniline (PANi) was prepared. Firstly, surface modifications of AC were carried out using sulfuric acid/nitric acid and followed by sodium hydrosulfite/ammonia, resulting in nitro group functionalized AC and free amine group functionalized AC, respectively. Functionalized groups were confirmed by FTIR analysis. Then, PANi was deposited onto modified AC surface through oxidation polymerization of aniline using ammonium persulfate as an initiator. After that, AC-NO2/PANi composites (1:0.25 and 1:0.5) and AC-NH2-g-PANi (1:0.25 and 1:0.5) were prepared. SEM images revealed that PANi was successfully deposited onto modified AC surface due to polar-polar interaction (in case of AC-NO2) and grafting reaction (in case of AC-NH2). Interestingly, at low aniline concentration, PANi nanofiber was produced, resulting in PANi having the highest surface area. As a result, the PANi nanofiber on porous activated carbon electrode exhibited high EDL capacitance value of 242 F/g. In contrast, PANi granular form exhibited significantly decreased in EDL capacitance value.

One-Step Synthesis of the Polyaniline–Single-Walled Carbon Tubes Nanocomposite in Formic Acid and Its Electrochemical Properties

A one-step synthesis of a stable dispersion of nanocomposite consisting of polyaniline (PANI) and single-walled carbon nanotubes (SWCNTs) was carried out by the oxidative polymerization of aniline with benzoyl peroxide (PB) in concentrated formic acid (FA). Electrically conductive film coatings were obtained by direct application of this dispersion to an electrode. The coatings have high specific electrochemical capacitance and stability during prolonged cycling in an aprotic electrolyte (1 M LiBF4 in γ-butyrolactone).

The synthesis and antistatic, anticorrosive properties of polyaniline composite coating

In this paper, acrylic ester grafting epoxy (A-g-EP) with COOH functional groups was firstly designed and prepared. Then the PANI-A-g-EP composite was obtained through oxidation polymerization of aniline on A-g-EP macromolecular chains. PANI nanoparticles in the PANI-A-g-EP composite were dispersed uniformly due to the strong interactions between macromolecular carboxyl groups and PANI. The composite is characterized by FT-IR, UV–vis and cyclic voltammetry (CV). The effect of PANI content on the glass transition temperature (Tg) and the thermal decomposition temperature (Td) were studied. PANI-A-g-EP composite coating was fabricated by the solution casting. The results of surface resistance, anticorrosion performances of the composite coating demonstrate that the good anticorrosion property of A-g-EP coating is caused by the good wet adhesion. The anticorrosion mechanism of PANI in the PANI-A-g-EP composite coating is revealed to be the electron transmission and passivation catalysis.

New Opportunities of Atomic Force Microscopy Probes upon Polyaniline Functionalization

NSG01 industrial atomic force microscope probes were functionalized by the electrically conductive polymer, polyaniline, during in situ oxidative polymerization of aniline at the probe point, which was confirmed by scanning electron microscopy. The quality of the deposited polymer can be controlled by measuring the resonance frequency of the gauge during functionalization. The comparative test of the probes prior to and after functionalization was performed using a TGT01 calibration grate, as well as on a special polyaniline test layer with a complex nanosized morphology in the semicontact mode of surface relief study and the phase contrast mode. Local current spectroscopy showed that the functionalized probe can be converted repeatedly from the conducting to nonconducting state owing to a reversible change in the conductivity of the polymer coating.

New proton conducting membrane based on bacterial cellulose/polyaniline nanocomposite film impregnated with guanidinium-based ionic liquid

New protic ionic liquid N-butylguanidinium tetrafluoroborate (BG-BF4) has been synthesized by single-step method. The ionic liquid is thermally stable to at least 300 °C and has ionic conductivity value of 8⋅10−3 S/cm at room temperature increasing to 0.18 S/cm at 180 °C. To develop a new proton conducting membrane, the nano-fibrillar matrix of bacterial cellulose (BC) has been impregnated with BG-BF4. The composite BC/BG-BF4 membrane containing 80 wt% of ionic liquid was found to have tensile strength of 35 MPa and ionic conductivity of 4.5⋅10−4 S/cm at 180 °C. The high saturation of BC with protic ionic liquid to 95 wt% allowed obtain composite membrane with reduced tensile strength of 6 MPa but excellent ionic conductivity of 5.2⋅10−2 S/cm at 180 °C. The deposition of polyaniline (PANI, emeraldine base) into BC matrix by oxidative polymerization of aniline on the surface of cellulose nanofibrils was found to improve the ionic conductivity of BC/BG-BF4 system significantly, reaching the value of 4⋅10−3 S/cm at 180 °C for cellulose film containing 80 wt% of ionic liquid. According to results of dynamical mechanical analysis (DMA), both BC/BG-BF4 and BC/PANI/BG-BF4 composites keep excellent storage modulus values at 180 °C (1000 MPa and 835 MPa, respectively). Due to the excellent holding capacity of BC matrix to ionic liquid, as well as good thermal and mechanical properties of BC/BG-BF4 composite it can be promising material for the fabrication of proton conducting membranes for fuel cells operating at elevated temperatures in water free conditions.

Polyaniline/FeZSM-5 composites – Synthesis, characterization and their high catalytic activity for the oxidative degradation of herbicide glyphosate

Semiconducting composites of nanostructured and granular polyaniline (PANI) with FeZSM-5 zeolite were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in water, without added acid and in an aqueous H2SO4 solution, in the presence of FeZSM-5, by using initial weight ratios aniline/FeZSM-5 of 1/1 and 1/5. These novel composite materials, in their as-synthesized (protonated) and deprotonated forms, were characterized by elemental, thermogravimetric and differential thermal analysis, scanning electron microscopy, FTIR and Raman spectroscopy, X-ray powder diffraction and conductivity measurements. The catalytic activity of the PANI/FeZSM-5 composites towards the oxidation of herbicide glyphosate with hydrogen peroxide has been investigated. A significant improvement of the catalytic activity of PANI/FeZSM-5 composites compared to that of pure PANI and FeZSM-5 was observed, manifested by the almost one order of magnitude more efficient oxidative degradation of glyphosate with hydrogen peroxide. The maximum of oxidized/decomposed amount of glyphosate was achieved in the presence of PANI/FeZSM-5 composite synthesized using an initial aniline/FeZSM-5 = 1/5 wt ratio. It has been shown that the method of synthesis and interactions between PANI and zeolite in this complex composite system, leading to more efficient electron transfer and hydrogen peroxide decomposition, are crucial for the catalytic properties of tested PANI/FeZSM-5 materials. It is shown that new PANI/FeZSM-5 composites present advanced catalyst materials for enhanced green catalytic degradation of pesticide/herbicide pollutants in environmental remediation systems.

Novel Free-Radical Scavengers Based on Ferrofluid/Polyaniline Nanocomposites

We investigated the antioxidant activity of novel ferrofluid/polyaniline nanocomposites with various mass ratios synthesized via in situ chemical oxidative polymerization of aniline without stirring in the presence of stabilized Fe3O4 nanoparticles and citric acid as a surfactant. The structural, morphological, thermal, magnetic, and electrical properties of the nanocomposites were characterized by IR and UV spectroscopy, XRD, SEM, TEM, TGA, VSM, and four-point-probe methods. The antioxidant potency was determined by modified 2,2-diphenyl-1-picrylhydrazyl (DPPH) method using an in vitro system. The DPPH free-radical scavenging tests of nanocomposites showed that their antioxidant properties depended on the amount of polyaniline in the composition. Results of the comparison of DPPH scavenging capacity of nanofiber polyaniline and granular ferrofluid/polyaniline nanocomposite show that the antioxidant activity is related to the morphology of polyaniline.