Catalytic oxidization polymerization of aniline in an H2O2?Fe2+ system

Polyaniline is prepared by chemical polymerization of aniline in an acidic solution using H₂O₂ as an oxidant and ferrous chloride as a catalyst. A wide variety of synthesis parameters are studied, such as the amount of the catalyst, reaction temperature, reaction time, initial molar ratio of oxidant, monomer and catalyst, and aniline and HCl concentrations. The polymerization of aniline can be initiated by a very small amount of catalyst. The yield and the conductivity of product depend on the initial molar ratio of the oxidant and monomer. The polyaniline with a conductivity of about 10° S/cm and a yield of 60% is prepared under optimum conditions. The process of polymerization was studied by in situ ultraviolet–visible spectroscopy and open‐circuit potential technology. Compared to the polymerization process in a (NH₄)₂S₂O₈ system, the features of the H₂O₂ Fe²⁺ system are pointed out, and the chain growth mechanism is proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1077–1084, 1999     

Magnetic and conducting Fe3O4–polypyrrole nanoparticles with core‐shell structure

Magnetic and conducting Fe₃O₄–polypyrrole nanoparticles with core‐shell structure were prepared in the presence of Fe₃O₄ magnetic fluid in aqueous solution containing sodium dodecylbenzenesulfonate (NaDS) as a surfactant and dopant. Both the conductivity and magnetization of the composites depend strongly on the Fe₃O₄ content and the doping degree. With increase of Fe₃O₄ content in the composite, the conductivity at room temperature decreases, but the saturated magnetization and coercive force increase. Transmission electron microscopy (TEM) images of Fe₃O₄ and Fe₃O₄–polypyrrole particles show almost spherical particles with diameters ranging from 20 to 30 and 30 to 40 nm, respectively. The thermal stability of Fe₃O₄–polypyrrole composites is higher than that of pure polypyrrole. Studies of IR, UV–visible and X‐ray photoelectron spectroscopy (XPS) spectra suggest that the increased thermal stability may be due to interactions between Fe₃O₄ particles and polypyrrole backbone. Copyright © 2003 Society of Chemical Industry     

Synthesis and formation mechanism study of rectangular-sectioned polypyrrole micro/nanotubules

Aligned polypyrrole (PPy) micro/nanotubules were synthesized via a self-assembly method using FeCl₃ as oxidant and Acid Red 1 (C.I. 18050, 5-(acetylamino)-4-hydroxy-3-(phenylazo)-2,7-naphthalenedisulfonic acid) as dopant. PPy has a typical length of 530 μm and a unique rectangular-sectioned morphology. Its general morphology could be manipulated by varying synthetic conditions including polymerization time, monomer concentration, oxidant species, and stirring. The synthesized PPy and reaction intermediates were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and solubility tests in methanol and water. Our observation and results suggest a plausible formation mechanism of rectangular-sectioned PPy micro/nanotubules. AR1-Fe(II) complex formed from the complexation of Acid Red 1 and Fe²⁺(reduced from Fe³⁺), which precipitated in the aqueous solution, might have functioned as ‘template’ during the polymerization of pyrrole monomers. The conductivity of PPy with different morphologies was also measured and compared.     

Preparation of conductive polypyrrole composites by in‐situ polymerization

Two kinds of conductive polypyrrole composites were prepared by in‐situ polymerization of pyrrole in a suspension of chlorinated polyethylene powder or in a natural rubber latex using ferric chloride as oxidizing agent. The preparation conditions were studied and the results showed that it is better to swell the chlorinated polyethylene powder with the monomer first, followed by addition of the oxidant, than to add the oxidant first, and that conversion can reach 98% for 6 h at room temperature. The conductivity percolation threshold of the composite is about 12%. The composites can be processed repeatedly, exhibiting a maximum tensile strength over 9 MPa and a maximum conductivity near 1 S cm⁻¹. The polypyrrole/natural rubber composites were prepared successfully by using a nonionic surfactant (Peregal O) as stabilizer at pH less than 3 with a molar ratio of FeCl₃/pyrrole = 2.5 below 45 °C. The latter composites show a low conductivity percolation threshold about 6%, a maximum tensile strength over 10 MPa and a maximum conductivity over 2 S cm⁻¹. The composites were characterized by FTIR and TGA. The polypyrrole/chlorinated polyethylene composites are very stable in air and almost no decrease of conductivity was observed for over 10 months examined. © 1999 Society of Chemical Industry     

超声法辅助合成苯偶酰

研究超声波辅助合成苯偶酰的反应条件,实验表明,以冰醋酸为溶剂,三氯化铁作为氧化剂,在超声频率53 kHz,反应温度60℃,反应40 min条件下,可获得75.2%产率,为实验室合成苯偶酰提供了有效方法。     

Chemical synthesis,characterization, and direct‐current conductivity studies of polypyrrole/γ‐Fe2O3 composites

The in situ polymerization of pyrrole was carried out in the presence of γ‐Fe₂O₃ to synthesize polypyrrole/γ‐Fe₂O₃ composites by a chemical oxidation method. The polypyrrole/γ‐Fe₂O₃ composites were synthesized with various compositions, including 10, 20, 30, 40, and 50 wt % γ‐Fe₂O₃ in pyrrole. The polypyrrole/γ‐Fe₂O₃ composites were characterized with X‐ray diffractometry and infrared spectroscopy. The surface morphology of these composites was studied with scanning electron microscopy. The direct‐current conductivity was studied from 40 to 200°C. The dimensions of the γ‐Fe₂O₃ particles in the matrix had a greater influence on the conductivity values. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2797–2801, 2007     

Iron(III) Chloride‐Catalysed Aerobic Reduction of Olefins using Aqueous Hydrazine at Ambient Temperature

A chemoselective reduction of olefins and acetylenes is demonstrated by employing catalytic amounts of ferric chloride hexahydrate (FeCl₃⋅6 H₂O) and aqueous hydrazine (NH₂NH₂⋅H₂O) as hydrogen source at room temperature. The reduction is chemoselective and tolerates a variety of reducible functional groups. Unlike other metal‐catalysed reduction methods, the present method employs a minimum amount of aqueous hydrazine (1.5–2 equiv.). Also, the scope of this method is demonstrated in the synthesis of ibuprofen in aqueous medium.     

Polyaniline/FE3O4 magnetic nanocomposite prepared by ultrasonic irradiation

Ultrasonic irradiation is employed to assist the chemical oxidative polymerization of aniline in the presence of Fe₃O₄ nanoparticles in order to prepare a polyaniline (PANI)/Fe₃O₄ magnetic nanocomposite. In the chemical oxidative polymerization of aniline in the initially neutral medium, the optimum molar ratio of the oxidant ammonium persulfate to the monomer aniline is 2 : 1. The prepared PANI is in the emeraldine form and is doped by sulfate anions. Fe₃O₄ particles are encapsulated by PANI and dispersed well in PANI. Fe₃O₄ increases the doping level and decreases the crystallinity of PANI. The PANI/Fe₃O₄ nanocomposite possesses conductivity and magnetic properties. Increasing the Fe₃O₄ content increases the magnetization of the PANI/Fe₃O₄ composite but decreases its conductivity. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2107–2111, 2006     

Fabrication of core-shell Fe3O4/polypyrrole and hollow polypyrrole microspheres

A facile synthesis of highly-regulated core-shell Fe₃O₄/polypyrrole (PPy) microspheres is achieved using a surfactant directed chemical oxidation polymerization in aqueous solution. The thickness of the PPy layer can be tuned by the quantity of the pyrrole monomer. The formation of core-shell Fe₃O₄/PPy microspheres lies on the static interactions between the SO₃⁻ group in sodium dodecyl sulphate molecules and Fe₃O₄ microspheres. Other surfactants such as cetyltrimethylammonium bromide and polyoxyethylene (10) isooctylcyclohexyl ether (Triton X-100) directed polymerization cannot produce such highly-regulated core-shell Fe₃O₄/PPy microspheres. XPS spectra proved the core-shell structure of the composite microspheres. XRD, FTIR, and UV–vis spectra are used to characterize the chemical structure of the composite microspheres. The electrical and magnetic properties are also investigated. Moreover, the obtained core-shell Fe₃O₄/PPy microspheres can be converted to highly-regulated hollow PPy microspheres by dissolving the Fe₃O₄ core with acid solution. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Chemically oxidized polypyrrole: Influence of the experimental conditions on its electrical conductivity and morphology

The effect of synthesis conditions on the electrical conductivity and the morphology of a chemically oxidized polypyrrole was investigated. It was found that the electrical conductivity of polypyrrole was strongly dependent on the pyrrole/FeCl₃ ratio, which controls the redox potential of the reaction medium. The reaction temperature and the reaction duration also influence the electrical conductivity of the polypyrrole. A considerable influence of the nature of the solvent used on the aggregation state of polypyrrole particles was demonstrated. Optimal experimental conditions are proposed.     

Preparation and characterization of polypyrrole nanocomposites by using various surfactants and Fe2O3 nanoparticles in aqueous media

Polypyrrole and its nanocomposites were obtained by chemical polymerization by using anhydrous ferric chloride as an oxidant in the presence of dodecylbenzensulfonate and poly(vinyl alchohol) as surfactants and iron (III) oxide nanoparticles in aqueous media. The products were characterized, such as morphology, chemical structure, and crystalline nature, by using analysis by scanning electron microscope, Fourier‐transform infrared spectrometry, and X‐ray diffraction. The results indicated that sodium dodecylbenzene‐sulfonate, poly(vinyl alcohol), and Fe₂O₃ nanoparticles influenced the properties of products. Scanning electron microscope analysis results indicated that when additives were added to the pyrrole matrix, the size of the product decreased and homogeneity increased. Fourier‐transform infrared spectrometry confirmed that nanocomposites formed in the presence of surfactant. X‐ray diffraction pattern analysis confirmed the presence of Fe₂O₃ nanoparticles in the nanocomposite matrix. J. VINYL ADDIT. TECHNOL., 22:362–367, 2016. © 2014 Society of Plastics Engineers     

Preparation of polypyrrole–polyurethane composite foam by vapor phase oxidative polymerization

Conductive polypyrrole–polyurethane composite foam was prepared by vapor phase polymerization of pyrrole on polyurethane foam using mixtures of FeCl₂ and FeCl₃ as oxidants. With increase in the FeCl₂/FeCl₃ ratio, the conductivity of the composite foam increased in spite of the decrease in polypyrrole content in the composite foam. Both conductivity and polypyrrole content increased with increase in the oxidant content in polyurethane. The conductivity of the composite foam is also a function of reaction temperature, and lower reaction temperatures were preferable for higher conductivity. The composite foam exhibited tensile strength and elongation comparable to those of pristine polyurethane foam. © 1995 John Wiley & Sons, Inc.     

Oxidative chemical polymerization of 3, 4‐ethylenedioxythiophene and its applications in antistatic coatings

The oxidative chemical polymerization of 3, 4‐ethylenedioxythiophene (EDOT) was conducted at room temperature in the presence of poly(styrene sulfonate) (PSS) as the doping agent, sodium supersulphate (Na₂S₂O₈) and ferric sulphate(Fe₂(SO₄)₃) as the compound oxidant and deionized water as the solvent. In order to remove sodium ion (Na⁺), ferric ion (Fe³⁺), and sulfate ion (SO4^2?), certain amount of ion exchanger was added after 24 h, the dark blue poly(3, 4‐ethylenedioxythiophene) (PEDT)/PSS solution was obtained. The influence of different proportions of EDOT and PSS, different proportions of EDOT and the compound oxidant, different stirring rates on the morphology, and surface resistivity were discussed. The influence of pH value of the PEDT/PSS solution, the coating thickness, and soak time on the surface resistivity was investigated. Recipe and experimental conditions were optimized and the PEDT/PSS solution was obtained with excellent performance which has relatively low in surface resistance, good water tolerance, and light transmittance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A facile and rapid synthesis of unsubstituted polythiophene with high electrical conductivity using binary organic solvents

Dichloromethane and acetonitrile containing thiophene and oxidant, respectively, were adopted as a binary organic solvent for oxidative synthesis of unsubstituted polythiophene (UPTh) under various conditions, i.e., oxidant/monomer molar ratio, polymerization temperature, and reaction time. We also investigated the effects of polymerization medium on the chemical and physical properties of the UPTh. The electrical conductivities of the UPThs polymerized in only acetonitrile or aqueous medium were 1.0 × 10⁻⁴ Scm⁻¹ and zero, respectively. However, the UPTh obtained in binary organic solvent system exhibited the highest electrical conductivity of 20.1 Scm⁻¹ without post-doping process under an oxidant/monomer molar ratio of 5:1 and a reaction time of 0.2 h at 0 °C. Furthermore, it showed an enhanced crystalline structure, thermal stability, and longer π-conjugation length than those in acetonitrile or aqueous medium. We also found that the presence of water as a polymerization medium inevitably gave rise to the incorporation of hydroxyl and carbonyl groups into the UPTh main chains by nucleophilic attack of water molecules. Therefore, these undesired structures broke the conjugated structures, resulting in UPTh with an electrically non-conducting property. The morphology of UPTh prepared in binary organic solvent appeared to be an aggregate of nanoparticles (50-200 nm). The combination of organic solvents should provide another systematic approach to the facile and rapid synthesis of UPThs with high conductivity.     

Thin polypyrrole films prepared by chemical oxidative polymerization

Polypyrrole (PPY) films with a thickness of 3–4 μm were obtained by chemical oxidation of pyrrole (PY) at the interface of chloroform and water with an oxidant (NH₄)₂S₂O₈. The films were compact and could be removed with a solid plate. The quality and compositions of these films varied with the molar ratios of the monomer and oxidant of the reaction systems. Overoxidation of polypyrrole was observed and confirmed by the characterizations via infrared spectra and elemental analysis of the films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2169–2172, 1998     

Copolymerization of aniline and vinyl acetate by using various surfactants in aqueous media

Polyaniline/poly(vinyl acetate) (PAn/PVAc) copolymer was prepared in aqueous solution by the copolymerization of vinyl acetate and aniline using a mixture of KIO₃ and (NH₄)₂S₂O₈ as an oxidant in the presence of the surfactants sodium dodecylbenzenesulfonate, poly(ethylene glycol), and hydroxypropylcellulose. The PAn/PVAc copolymers were characterized in terms of their conductivity, morphology, and structure. The results indicated that the morphology and conductivity of the products were dependent on the type of surfactant used (anionic or nonionic). Furthermore, it was found that adding vinyl acetate monomer to the stirred aqueous solution containing oxidant, surfactant, and aniline monomer had a great effect on the morphology and increased the amount of the product. The structures of the products were determined by FTIR spectroscopy. J. VINYL ADDIT. TECHNOL., 13:229–233, 2007. © 2007 Society of Plastics Engineers     

Characterization and physical properties investigation of conducting polypyrrole/TiO2 nanocomposites prepared through a one‐step “in situ” polymerization method

Nowadays, nanocomposites are a special class of materials having unique physical properties and wide application potential in diverse areas. The present research work describes an efficient method for synthesis of a series of polypyrrole/titanium dioxide (PPy/TiO₂) nanocomposites with different TiO₂ ratios. These nanocomposites were prepared by one‐step in situ deposition oxidative polymerization of pyrrole hydrochloride using ferric chloride (FeCl₃) as an oxidant in the presence of ultra fine grade powder of anatase TiO₂ nanoparticles cooled in an ice bath. The obtained nanocomposites were characterized by Fourier‐transform infrared (FTIR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and scanning electron microscope (SEM) techniques. The obtained results showed that TiO₂ nanoparticles have been encapsulated by PPy with a strong effect on the morphology of PPy/TiO₂ nanocomposites. Also, the synthesized PPy/TiO₂ nanocomposites had higher thermal stability than that of pure PPy. The investigation of electrical conductivity of nanocomposites by four‐point probe instrument showed that the conductivity of nanocomposite at low TiO₂ content is much higher than of neat PPy, while with the increasing contents of TiO₂, the conductivity decreases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sintering and conductivity of Sc-doped CaZrO3 with Fe2O3 as a sintering aid

This paper reports the effect of 0.1–0.5 wt% Fe₂O₃ addition on sintering and electrical properties of CaZr_0.95Sc_0.05O_3-δ ceramics synthesized by combustion method. Addition of the sintering aid was shown to enhance ceramic densification and grain coarsening at a reduced sintering temperature and a shorter holding time (1430 °C, 2 h). Effect of the sintering aid on electrical conductivity of the ceramics was investigated using impedance spectroscopy. The highest total conductivity was achieved for the composition with 0.5 wt% Fe₂O₃; it was about an order of magnitude higher than that of the composition without Fe₂O₃. The effect of Fe₂O₃ addition on the conductivity of the grain interior and grain boundaries has been discussed. It was concluded that ceramic densification, grain coarsening and formation of small amounts of calcium ferrite at the grain boundaries upon Fe₂O₃ addition were responsible for the conductivity enhancement.     

Oxidative dissolution of pyrite in acidic media

The pyrite oxidative dissolution in air-saturated (AS), H₂O₂, and Fe³⁺ solutions at pH 2.5 and 25 °C was investigated by electrochemical and aqueous batch experiments. The corrosion current density (i _corr) increases from AS solution to Fe³⁺ and H₂O₂ solutions. For the same oxidant, i _corr increases when the concentration of the oxidant increases. Similar variation was observed for the corrosion potential (E _corr). Electrochemical impedance spectroscopy measurements have indicated that in AS and H₂O₂ solutions, the charge transfer is the rate determining step of pyrite oxidative dissolution. In the presence of Fe _(aq) ³⁺ , both the charge transfer process and mass transfer caused by the diffusion of oxidant or reaction products across the interface of electrode control the mineral oxidative dissolution. The corrosion current densities of oxidative dissolution measured by electrochemical methods are higher than those estimated from dissolution rates determined by aqueous bath experiments. The observed differences suggest that the mechanism of polarized electrode oxidation is different by the mechanism of pyrite oxidation under open circuit conditions.     

Preparation and characterization of conductive and magnetic PPy/Fe3O4/Ag nanocomposites

In this article, conductive and magnetic nanocomposites composed of polypyrrole (PPy), magnetite (Fe₃O₄) nanoparticles (NPs), silver (Ag) NPs, have been successfully synthesized with a two step process. First, the PPy/Fe₃O₄ was prepared by the ultrasonic in situ polymerization. Next, the PPy/Fe₃O₄/Ag was synthesized through the electrostatic adsorption. The products were characterized by fourier‐transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), Thermogravimetric (TG), conductivity and magnetization analysis, and the results showed that the Ag NPs with the good conductivity coated uniformly on the surface of PPy/Fe₃O₄ and improved the conductivity of PPy/Fe₃O₄/Ag composites. In addition, as compared with PPy/Fe₃O₄, PPy/Fe₃O₄/Ag composites also have the excellent electro‐magnetic property and enhanced thermostability. POLYM. COMPOS., 35:450–455, 2014. © 2013 Society of Plastics Engineers