A comparative study of water dispersible polyaniline nanocomposites prepared by laccase‐catalyzed and chemical methods

A comparative study of chemical and enzymatic methods of aniline polymerization was carried out. Fungal laccase from Trametes hirsuta was used in the synthesis of polyaniline nanoparticles made with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS). Template polymerization of aniline was carried out in aqueous buffer. It was shown that the laccase had high long‐term and operating stabilities under acidic condition favorable for synthesis of conducting polyaniline. UV‐vis, FTIR spectroscopy, and cyclic voltammetry analysis are used for the characterization of the polyelectrolyte complexes of polyaniline and PAMPS. The incorporation of the polymeric acid in polyaniline has been demonstrated by atomic force microscopy. The size and morphology of the nanoparticles of the polyaniline–PAMPS complexes depended on the method of the synthesis. A comparison of some physical and chemical properties of water dispersible conducting polyaniline–PAMPS was performed under production by enzymatic and chemical methods. It was found a difference in structures and some physicochemical properties of polyaniline colloids prepared by chemical and laccase‐catalyzed methods. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of chemical polymerization conditions on the properties of polyaniline

The chemical polymerization of aniline in aqueous solutions was studied as a function of a wide variety of synthesis parameters, such as pH, relative concentration of reactants, polymerization temperature and time, etc. The polymer was synthesized using a number of different oxidizing agents and different protonic acids. It was found that the reaction yield was not sensitive to most variables. By contrast, the inherent viscosity of the polymer, measured in solutions in concentrated sulphuric acid, was strongly dependent on the synthesis parameters. Optimum reaction conditions are outlined for the chemical polymerization of aniline, for post-treatment with aqueous HCl solutions, and for compensation of the emeraldine salt into its base form. Under such conditions, high-quality polyaniline base was synthesized with an inherent viscosity (0.1% w/w polymer in sulphuric acid) as high as 2.32 dl g⁻¹.     

有机/无机酸复合掺杂导电聚苯胺的合成及性能研究

采用化学氧化聚合法以苯胺为单体,过硫酸胺为氧化剂,在有机/无机混合酸的水溶液中合成导电聚苯胺.考察了有机/无机混合酸对聚苯胺性能的影响,并通过四探针、差热分析、红外光谱及拉曼光谱研究聚苯胺掺杂前后结构的变化.结果表明,当聚合温度为20℃、磺基水杨酸和硫酸的摩尔浓度比为0.25:1时,掺杂态聚苯胺电导率和溶解度达到最大值;其中电导率可达13.5 S·cm~(-1),在氮甲基吡咯烷酮(NMP)中溶解度可达85%.差热分析表明,有机/无机酸复合掺杂聚苯胺热稳定性较单一酸掺杂聚苯胺热稳定性有很大的提高;红外光谱和拉曼光谱表明;掺杂后聚苯胺具有导电性是因为其分子链上电荷离域形成了共轭结构.     

Characterization of polyaniline/Ag nanocomposites using H2O2 and ultrasound radiation for enhancing rate

Polyaniline/Ag nanocomposites have been synthesized via in situ chemical oxidation polymerization of aniline in silver salt by sonochemical method using H₂O₂ as an external medium. H₂O₂ was used to reduce AgNO₃ to Ag nanoparticles as well as to polymerize aniline to polyaniline in the same pot. The ultrasound radiation as an energy source was applied to facilitate the reaction by reducing the reaction time. Reduction of the silver salt in aqueous aniline leads to the formation of silver nanoparticles which in turn catalyze oxidation of aniline to polyaniline. The research on the structures and properties of the composites showed the individual or aggregated silver nanoparticles are dispersed in the matrix of polyaniline. The composites possess a higher degradation temperature than polyaniline alone, and their electrical conductivity are raised morethan 200 times. The cyclic voltammetry and impedance spectroscopy results showed that the polyaniline/Ag film exhibits considerably higher electroactivity compared with polyaniline film without Ag particles. POLYM. COMPOS., 31:1662–1668, 2010. © 2009 Society of Plastics Engineers     

Oxidative degradation of polyaniline during the chemical oxidative polymerization of aniline in aqueous methanol medium

The course of chemical oxidative polymerization of aniline using ammonium persulfate as the initiator in acidic (1 M HCl) aqueous methanol (30 to 70 vol%) was studied spectrophotometrically. It was found that at temperatures greater than about 10 °C the reaction leads to degradation of polyaniline, the effect being greater with increasing methanol concentration. This is quite unlike the situation in aqueous ethanol where the product is the usual emeraldine hydrochloride form of polyaniline. Copyright © 2005 Society of Chemical Industry     

Didecyl ester of 4‐sulfophthalic acid as a plast dopant and emulsifier in the chemical polymerization of aniline into polyaniline salt

Polyaniline salt was synthesized through the chemical oxidation of aniline with sodium persulfate as the oxidant and didecyl ester of 4‐sulfophthalic acid via three different polymerization pathways (aqueous, emulsion, and interfacial). In these polymerization processes, the ester acted as a novel plast dopant and as an emulsifier. The yield, conductivity, and number of ester units present in the polyaniline salts were determined. A polyaniline salt prepared by emulsion polymerization was soluble in chloroform and showed excellent solution‐processing properties. Polyaniline samples prepared by aqueous or interfacial polymerization were not soluble in chloroform. A soluble polyaniline salt was successfully synthesized through the washing of an organic layer containing the polyaniline salt with water in emulsion polymerization. X‐ray diffraction spectra of polyaniline salts prepared by the three different methods showed an ordered, layer‐type supramolecular structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

合成条件对聚苯胺成纤性能的影响

以苯胺为单体、过硫酸铵为氧化剂、在盐酸水溶液中化学法合成聚苯胺 ,研究的重点是确立一个能够适合纺丝要求的合成参数体系。合成的聚苯胺重均相对分子质量达 2 9× 10 4。以不同条件下合成的聚苯胺为原料湿法纺制了聚苯胺导电纤维。     

Synthesis of exfoliated polyaniline–clay nanocomposite in supercritical CO2

This paper presents the works done to synthesize fully exfoliated polyaniline–clay nanocomposites (PCNs) with high purity via in situ polymerization of aniline in Cloisite 30B nano-clay suspension in supercritical CO₂ (ScCO₂) medium. The Cloisite 30B was first delaminated with ScCO₂ treatment in the presence of aniline monomers. Ammonium peroxydisulfate (APS) solution was added rapidly into the mixture of delaminated Cloisite 30B and aniline monomers to produce PCNs. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and XRD analysis have been used to characterize the morphology and structure of the as-synthesized product. SEM results reveal that nano-clays are fully exfoliated in the final nanocomposite which is synthesized in ScCO₂. FTIR and UV–vis analysis showed that the resulted polyaniline (PANI) had been in highly conductive emeraldine salt state and ScCO₂ does not have any effect on chemical structures of the PANI.     

Electrochemical synthesis of polyaniline in the presence of poly(amidosulfonic acid)s with different rigidity of polymer backbone and characterization of the films obtained

We have studied electrochemical matrix polymerization of aniline in the presence of poly(amidosulfonic acid)s of different nature: poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (PAMPSA, flexible backbone); poly(p,p′-(2,2′-disulfoacid)-diphenylene-iso-phthalamid) (i-PASA, semi-rigid backbone); poly(p,p′-(2,2′-disulfoacid)-diphelylene-tere-phthalamid) (t-PASA, rigid backbone). Also, we have investigated spectral and electrochemical properties of the films obtained, as well as their surface morphology. The matrix polymerization results in the formation of interpolymer complexes of polyaniline (PANI) and the above-cited polyacids. The acceleration of aniline electropolymerization in the presence of poly(amidosulfonic acid)s was observed due to association of aniline molecules to sulfonic groups of the polyacid and higher local concentration of protons near the polyacid backbone. The rigid-chain polyacids interfere with the normal course of the electropolymerization, which manifests itself in the changes of the shape of time dependences of absorbance and charge. Cyclic voltammetry and spectroelectrochemical experiments showed that the formation of interpolymer complex with rigid-chain polyacids distorts spectroelectrochemical characteristics of PANI. This evidently results from steric hindrances in the formation of quinoid units.     

Ring‐opening polymerization of caprolactone using novel polyaniline salt catalyst

Hybrid composite of polyaniline metal oxide composite, polyaniline‐dodecyl hydrogen sulfate salt with ferric oxide, was prepared for the first time via simple one‐step process of oxidizing aniline with ferric tris(dodecyl sulfate). Ferric tris(dodecyl sulfate) acts as an oxidant, emulsifier, dopant for polyaniline and also source of ferric oxide. Polyaniline salt composites were prepared via aqueous, emulsion, and interfacial polymerization pathways. Polyaniline salt composite was successfully demonstrated as polymer based solid acid catalysts in the ring‐opening polymerization of ε‐caprolactone for the first time. This methodology gave low molecular weight poly(ε‐caprolactone) (MW‐4035) with highly crystalline polymer of flower petals like morphology in 52 wt% yield (with respect to the amount of ε‐caprolactone used). Advantages of this methodology are the use of easily synthesizable, easily handlable, recyclable, cheaper, and eco‐friendly nature of the catalyst. POLYM. ENG. SCI., 55:2245–2249, 2015. © 2015 Society of Plastics Engineers     

Electrochemical behaviors of polyaniline–poly(styrene‐sulfonic acid) complexes and related films

This research focuses on the syntheses of polyaniline with poly(styrenesulfonic acid) and their electrochemical behavior, including absorbance behavior and electrochemical response time of polyaniline‐poly(styrenesulfonic acid) [PANI–PSSA]. The complexes PANI–PSSA were prepared by electrochemical polymerization of monomer (aniline) with PSSA, using indium‐tin oxide (ITO) as working electrode in 1M HCl solution. Polyaniline (PANI), poly(o‐phenetidine)–poly(styrenesulfonic acid) [POP–PSSA], and poly(2‐ethylaniline)–poly(styrenesulfonic acid) [P2E‐PSSA] also were prepared by electrochemical polymerization and to be the reference samples. The products were characterized by IR, VIS, EPR, water solubility, elemental analysis, conductivity, SEM, and TEM. IR spectral studies shows that the structure of PANI–PSSA complexes is similar to that of polyaniline. EPR and visible spectra indicate the formation of polarons. The morphology of the blend were investigated by SEM and TEM, which indicate the conducting component and electrically conductive property of the polymer complexes. Elemental analysis results show that PANI–PSSA has a nitrogen to sulfur ratio (N/S) of 38%, lower than that for POP–PSSA (52%) and P2E–PSSA (41%). Conductivity of the complexes are around 10^?2 S/cm, solubility of PANI–PSSA in water is 3.1 g/L. The UV‐Vis. absorbance spectra of the hybrid organic/inorganic complementary electro‐chromic device (ECD), comprising a polyaniline–poly(styrenesulfonic acid) [PANI–PSSA] complexes and tungsten oxide (WO₃) thin film coupled in combination with a polymer electrolyte poly(2‐acrylamido‐2‐methyl‐propane‐sulfonic acid) [PAMPSA]. PANI–PSSA microstructure surface images have been studied by AFM. By applying a potential of ～3.0 V across the two external ITO contacts, we are able to modulate the light absorption also in the UV‐Vis region (200–900 nm) wavelength region. For example, the absorption changes from 1.20 to 0.6 at 720 nm. The complexes PANI–PSSA, POP–PSSA, and P2E–PSSA were prepared by electrochemical polymerization of monomer (aniline, o‐phenetidine, or 2‐ethylaniline) with poly(styrenesulfonic acid), using ITO as working electrode in 1M HCl solution, respectively. UV‐Vis spectra measurements shows the evidences for the dopped polyaniline system to be a highly electrochemical response time, recorded at the temperature 298 K, and the results were further analyzed on the basis of the color‐ discolor model, which is a typical of protontation systems. Under the reaction time (3 s) and monomer (aniline, o‐phenetidine, 2‐ethylaniline) concentration (0.6M) with PSSA (0.15M), the best electrochemical color and discolor time of the PANI–PSSA is slower than POP–PSSA complexes (125/125 ms; thickness, 3.00 μm) and P2E–PSSA complexes. Under the same thickness (10 μm), the best electrochemical color and discolor time of the PANI–PSSA complexes is 1500/750 ms, that is much slower than P2E–PSSA complexes (750/500 ms) and POP–PSSA complexes (500/250 ms). In film growing rate, the PANI–PSSA complexes (0.54 μm/s) are slower than P2E–PSSA complexes (0.79 μm/s) and POP–PSSA complexes (1.00 μm/s), it can be attributed to the substituted polyaniline that presence of electro‐donating (? OC₂H₅ or ? C₂H₅₎ group present in aniline monomer. The EPR spectra of the samples were recorded both at 298 K and 77 K, and were further analyzed on the basis of the polaron–bipolaron model. The narrower line‐width of the substituted polyaniline complexes arises due to polarons; i.e., it is proposed that charge transport take place through both polarons and bipolarons, compared to their salts can be attributed to the lower degree of structural disorder, the oxygen absorption on the polymeric molecular complexes, and due to presence of electro‐donating (? OC₂H₅ or ? C₂H₅) group present in aniline monomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:4023–4044, 2006     

Preparation and characterization of soluble polyaniline

Polyaniline, which is soluble in common organic solvents, has been synthesized through the oxidative chemical polymerization of aniline in the presence of benzene diazonium chloride salt in an aqueous HCl acid medium. The blue‐black polyaniline thus prepared exists in a lower oxidation state than emeraldine. An X‐ray photoelectron spectroscopy study has shown that the intrinsic oxidation state of the polymer is 0.38. An elemental analysis has shown that the fractional doping level or degree of oxidation of the blue‐black polyaniline is 0.26. The product is believed to consist of a lower number of imine nitrogens in comparison with the polyemeraldine base. This fact is also corroborated by the lower electrical conductivity of the polymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Polymerization of Aniline Using Iron(III) Catalyst and Ozone,and Kinetics of Oxidation Reactions in the Catalytic System

The environmentally benign polymerization of aniline provided polyaniline with an emeraldine structure by using iron(III) and ozone which is easily converted from oxygen in air. The influence of the reaction temperature upon the molecular weight of the polyaniline in this system is different from that in the polymerization of aniline using ammonium peroxodisulfate as an oxidant. Although the polyaniline prepared here has low molecular weight, the low molecular weight of the polyaniline does not significantly influence the electrical conductivity of cast films. In contrast, this can provide an advantage for the engineering of polyaniline through solution‐processing. Kinetics of oxidation reactions in the polymerization, systematically investigated here, has revealed that polyaniline is produced catalytically in terms of iron(III) and that an oxidation reaction of iron(II) to iron(III) could be a rate‐determining step in the polymerization.     

Synthesis of sulfonated graphene/polyaniline composites with improved electroactivity

The sulfonation of graphene by coupling with the diazonium salts of sulfanilic (SA) acid and amino-4-hydroxy-2-naphthalenesulfonic (NSA) acid is studied. Coupling with the diazonium salt of NSA gives the highest degree of sulfonation. Composites of polyaniline (PANI) and sulfonated graphene (SG) are prepared by the polymerization of aniline in the presence of the SG. The materials have been characterized by Raman, Fourier transformed infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. These materials are electrochemically active at pHs close to physiological pH due to the doping of PANI with the sulfonic groups in SG trapped in the polymer. Furthermore, good conductivity values are obtained.     

Template polymerization of sodium methacrylate onto poly(allylamine) hydrochloride

The radical polymerization in aqueous solution of sodium methacrylate in the presence of poly(allylamine) hydrochloride as a template was studied using dilatometry. The properties of the polyelectrolyte complexes resulting from these template polymerizations were investigated and compared with those of the poly(sodium methacrylate)/poly(allylamine) hydrochloride complexes obtained by simple mixing of the preformed polymers. The kinetic study provides evidence for the presence of a strong template effect and indicates that the polymerization occurs by a zip mechanism. The results of the different characterization analyses have shown that the complexes obtained by template polymerization have a more ordered structure than the complexes prepared by mixing the two polymers.     

Exploration of the morphological transition phenomenon of polyaniline from microspheres to nanotubes in acid‐free aqueous 1‐propanol solution in a single polymerization process

Polyaniline micro‐ or nanostructures have been widely investigated due to their unique physical and chemical properties. Although several studies have reported the synthesis of polyaniline microspheres and nanotubes, their mechanisms of formation remain controversial. This study reports our observation of the morphological transition of polyaniline from microspheres to nanotubes in a single polymerization process and also tries to propose their mechanisms of formation. The polymerization of aniline monomer in acid‐free aqueous 1‐propanol solutions (1 and 2 mol L^?1) produces polyaniline microspheres and nanotubes at different reaction stages through a morphology transition process with treatment using ultrasound. In the initial reaction stage, Fourier transform infrared spectra indicate that the aniline monomers form phenazine‐like units, producing polyaniline microspheres with an outside diameter of 1–2 µm. The hydrogen bonds between 1‐propanol and polyaniline serve as the driving force for the polyaniline chains to build microspheres. As the reaction continues, observation indicates the microspheres decompose and reform one‐dimensional nanotubes. In this stage, a structure consisting of a head of phenazine‐like units and a tail of acid‐doping para‐linked aniline units develops. The protonation of the para‐linked aniline units provides the driving force for the formation of nanotubes through a self‐curling process. We report here the unique morphology transition of polyaniline from microspheres to nanotubes in a single polymerization process. The results indicate that the structural change of polyaniline leads to this morphological change. The mechanisms of formation of the microspheres and nanotubes in a polymerization process are also well explained. Copyright © 2010 Society of Chemical Industry     

Corrosion protection of magnesium ZM 21 alloy with polyaniline–TiO2 composite containing coatings

A polyaniline–TiO₂ composite (PTC) was prepared by oxidative polymerization of aniline in phosphoric acid with ammonium persulphate, in the presence of TiO₂. The composite was characterized by spectroscopic methods. An acrylic paint containing the PTC was prepared and the coating formed on magnesium alloy was evaluated by electrochemical impedance spectroscopy after exposure to salt spray test for a period of 250 h. The coating containing the PTC was found to protect the magnesium alloy more efficiently than the coating containing polyaniline.     

Synthesis and characterization of novel copper/polyaniline nanocomposite and application as a catalyst in the Wacker oxidation reaction

Copper nanoclusters were synthesized by a chemical reduction of an aqueous copper salt solution by sodium borohydride. A polyaniline nanocomposite containing copper nanoclusters was prepared by polymerizing a monomer aniline hydrochloride solution containing the copper nanoclusters using ammonium persulfate as an oxidizing agent. The synthesized nanocomposite was characterized using various techniques such as UV‐visible spectroscopy, FTIR spectroscopy, X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The presence of copper was confirmed by XRD and the size of the copper clusters was found to be ～53 nm, which is in good agreement with that obtained from the TEM. The synthesized nanocomposite was used to serve as a catalyst in a Wacker oxidation reaction for the conversion of 1‐decene to 2‐decanone in the presence of molecular oxygen. The formation of 2‐decanone was confirmed using GC‐MS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2412–2417, 2003     

Chemical synthesis of polyaniline in the presence of poly(amidosulfonic acids) with different rigidity of the polymer chain

Conducting polyaniline (PANI) was chemically synthesized in the presence of water-soluble aromatic polyamides containing sulfonic groups: poly-(p,p’-(2,2′-disulfonic acid)-diphenylene-tere-phthalamide) (t-PASA, rigid backbone), poly-(p,p’-(2,2′-disulfonic acid)-diphenylene-iso-phthalamide) (i-PASA, semi-rigid backbone) and their copolymer (co-PASA) with the monomers ratio 1:1, as well as in the presence of flexible-backbone polyacids: poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) and poly(styrene sulfonic acid) (PSSA). In these conditions the matrix polymerization of aniline results in the formation of water-soluble interpolymer complexes of PANI with the above cited polyacids. The character of spectral changes in the UV, visible and near IR (UV-Vis-NIR) range during the synthesis and the polymerization rates depend strictly on the structure of polyacid matrix. Higher flexibility of the polyacid backbone (PAMPSA, PSSA) contributes to higher relative absorption of localized polarons (750 nm), while in the spectrum of interpolymer complexes with rigid-chain polyacid (t-PASA) the absorption of delocalized polarons (1300-1500 nm) prevails. The complexes with semi-flexible i-PASA and co-PASA exhibit intermediate behavior. The results are interpreted in terms of differences in the inter-chain interactions in the interpolymer complexes of different structure. Fourier transform infrared (FTIR) spectroscopy data support the assumption of the incorporation of the polyacids in the PANI through an interaction between sulfonic groups of the polyacids and nitrogen atoms of PANI. Spectroelectrochemical and electrochemical (cyclic voltammetry) studies of the films cast from the obtained solutions showed that the formation of quinoid units at high oxidation level is retarded in the interpolymer complexes of PANI with rigid- and semi-rigid-chain polyacids. Atomic force microscopy (AFM) and direct current (DC)-conductivity data are also presented.     

Simplifying the reaction system for the preparation of polyaniline nanofibers: Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media

In this study, several polyaniline samples were prepared by oxidative chemical polymerization using only aniline, (NH₄)₂S₂O₈ and HCl in aqueous media at room temperature for morphological studies by SEM (scanning electron microscopy). The results show that polyaniline nanofibers can be obtained by template-free oxidative chemical polymerization in a conventional low-pH acidic aqueous medium (pH ～ 0) at room temperature. The study indicates that it is crucial to employ a mild post-polymerization processing procedure, such as dialysis, to preserve the as-formed morphology of polyaniline nanofibers. Our study also suggests that polyaniline could adopt the nanofiber structure as its intrinsic morphology when it is synthesized in a simple oxidative chemical polymerization system consisting of only aniline, (NH₄)₂S₂O₈ and HCl in an aqueous medium at room temperature.