The genesis of polyaniline nanotubes

Aniline has been oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. Protons are produced in the course of oxidation and the pH decreases as the reaction proceeds. The oxidation had two subsequent phases: (1) the oxidation of the neutral aniline molecules and the initially produced low-molecular weight aniline oligomers at low acidity, followed by (2) the oxidation of the anilinium cation after the acidity became higher. The two phases of oxidation gave different products, aniline oligomers with mixed ortho- and para-coupling of aniline molecules, and polyaniline nanotubes, respectively.The aniline oligomers are produced at first at low acidity, pH > 4, some of them as rod-like crystals. The molecular weight of the oligomers has been assessed by gel-permeation chromatography to be of several thousands. The 2-3 wt.% content of sulfur in deprotonated samples suggests that the oxidation products are partly sulfonated. The oxidation of ortho-coupled anilines combined with intramolecular cyclization produces phenazine units or their blocks, as indicated by FTIR spectra. A high-molecular weight polyaniline is produced at pH < 2. The protonation of the intermediate pernigraniline form of polyaniline is a prerequisite for the polymerization.The nano-sized oligomer crystallites serve as starting templates for the nucleation of PANI nanotubes. Further growth of nanotubes proceeds by the self-organization of the phenazine units or their blocks located at the ends of the PANI chains. Polyaniline nanotubes have a typical outer diameter of 100-200 nm, with a wall thickness of 50-100 nm, an inner diameter of 0-100 nm, and a length extending to several micrometres.     

Suspension polymerization of aniline hydrochloride in non‐aqueous media

The oxidation of aniline hydrochloride by ammonium peroxydisulfate in non‐aqueous media was studied, when the monomer or oxidant or both were not completely soluble. Polyaniline was formed in acetone, methanol and toluene. Aniline oligomers only were produced in chloroform and n‐butylacetate. No interaction of the monomer and the oxidant was observed in dimethylsulfoxide and N‐methylpyrrolidone. UV‐visible and Fourier transform infrared spectra were recorded in order to study the molecular structure of the final products. Conductivity was measured for conducting protonated forms and corresponding bases. An explanation of aniline hydrochloride oxidation in various organic media is offered. Copyright © 2011 Society of Chemical Industry     

The influence of decanethiol/4-aminothiophenol mixed monolayers on the electrodeposition of polyaniline thin films

Polyaniline thin films were electrodeposited onto naked Au and thiol-modified Au electrodes by potential cycling. Self-assembled monolayers (SAMs) contained 4-aminothiophenol (4-ATP) and n-decanethiol (DT) in varying molar ratios. The electropolymerization of aniline at these surfaces is strongly influenced by the composition of the monolayer. When the potential was cycled between 0 and 0.8 V, the polymerization of aniline initiated at 4-ATP sites in the SAMs. The electrical conductivity of the films was found to increase as the mole fraction of 4-ATP in the SAM increased. When the potential was cycled between 0 and 1.0 V, polymerization of aniline is initiated both at the surface and by the direct oxidation of aniline monomers in solution. Nevertheless, the composition of the SAM has a profound influence on the properties of the polyaniline films, especially the electrical conductivity, which increases with 4-ATP mole fraction up to a value of 0.77, and then decreases dramatically. The amount of 4-ATP in the SAM influences the rate of aniline oxidation, which determines the overall polymerization rate, and, in turn, influences the thin film conductivities. When the rate of monomer oxidation is too high, the films are over oxidized and lose conductivity. On the other hand, when the monomer oxidation rate is too low, the oligomer number suffers, and the conductivity drops. Thus, with respect to the electrical conductivity, there appears to be an optimum rate of aniline oxidation, which can be controlled by use of the appropriate SAM.     

A comparative study of the electrochemical/electro-degradation of polyaniline from aniline loaded in a clay-mineral/polyaniline composite matrix to that of the bulk solution

Polyaniline was electrodeposited on an insulating-host matrix, Bentonite (clay mineral). Cyclic voltammetry was used to characterize the electrochemical response. Results show that aniline was trapped in the Bentonite/Polyaniline composite matrix and that the rate of polyaniline electrodeposition from this trapped aniline is different from that of the bulk solution. The electrochemical degradation rates are also different.     

导电聚苯胺/聚乙烯醇复合乳液的制备研究

以聚乙烯醇为树脂基体 ,通过乳液氧化聚合同步搀杂有机酸 ,研究了聚苯胺 /聚乙烯醇复合乳液的制备。结果表明 ,过硫酸铵的用量对聚苯胺的产率影响较大 ,当氧化剂 /苯胺的摩尔比达到 2时 ,产率为95% ,高于溶液法的原料比例。十二烷基苯磺酸和聚乙烯醇 (88%醇解度 )对聚苯胺乳胶的粒径亦有影响。在聚苯胺 /聚乙烯醇复合膜中 ,当聚苯胺含量超过 2 0 %后 ,电导率趋向稳定 ,可达 2 .3 s/ cm     

Polyaniline‐supported acid catalyst: Esterification of cinnamic acid with alcohols

Polyaniline‐supported acid salts such as polyaniline‐hydrochloride, polyaniline‐sulfate, and polyaniline‐nitrate were prepared by oxidation of aniline using benzoyl peroxide and ammonium persulfate as oxidizing agents. Polyaniline salts were used as catalysts in the esterification of cinnamic acid with alcohols. Polyaniline‐sulfate salt was found to be the best catalyst for the esterification of cinnamic acid. The reusability, handling, and recovery of the catalyst were found to be good. The yield of the ester depended on the type of the polyaniline salt, amount of the catalyst, amount of alcohol, and both the time and the temperature of the reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1584–1590, 2005     

One-step synthesis of oriented polyaniline nanorods through electrochemical deposition

Summary Large-scale of oriented Polyaniline nanorods have been synthesized by one-step electrochemical deposition on aluminium electrode without the aid of any templates. The diameters and lengths of polyaniline nanorods are in the range of 50–60 nm and 150–250 nm, respectively. The morphologies and molecular structures of the film are characterized by field-emission scanning electron microscopy (FE-SEM), Ultraviolet-Visual (UV-vis) and Fourier transform infared (FTIR). The effects of synthetic parameters, such as the concentration of aniline and electric current intensity, on the morphologies of polyaniline films are investigated.     

聚苯胺溶解性研究

以苯胺氧化聚合和乳液聚合两种方法合成聚苯胺(PAn),研究了溶剂、聚合方法、反应温度、导电态、十二烷基苯磺酸用量等因素对聚苯胺溶解性的影响。结果表明,N-甲基吡咯烷酮是本征态聚苯胺的良溶剂,用乳液聚合法合成的聚苯胺其溶解性明显高于化学氧化法合成的聚苯胺,当乳液中十二烷基苯磺酸∶苯胺(摩尔比)=2.0∶1,聚合温度25℃时合成溶解率大的PAn。     

Polyaniline–silver composites prepared by the oxidation of aniline with silver nitrate in acetic acid solutions

The reaction between two non‐conducting chemicals, aniline and silver nitrate, yields a composite of two conducting components, polyaniline and metallic silver. Such conducting polymer composites combine the electrical properties of metals and the materials properties of polymers. In the present study, aniline was oxidized with silver nitrate in solutions of acetic acid; in this context, aniline oligomers are often a major component of the oxidation products. An insoluble precipitate of silver acetate is also present in the samples. The optimization of reaction conditions with respect to aniline and acetic acid concentrations leads to a conductivity of the composite as high as 8000 S cm^?1 at ca 70 wt% (ca 21 vol%) of silver. A sufficient concentration of acetic acid, as well as a time extending to several weeks, has to be provided for the successful polymerization of aniline. Polyaniline is present as nanotubes or nanobrushes composed of thin nanowires. The average size of the silver nanoparticles is 30–50 nm; silver nanowires are also observed. Copyright © 2009 Society of Chemical Industry     

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。     

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     

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     

Research on the preparation technology of polyaniline nanofiber based on high gravity chemical oxidative polymerization

Polyaniline (PANI) nanofibers with higher yield and homogeneous morphology were successfully prepared in larger scale by multi-step oxidation process with high gravity chemical oxidative polymerization (HGCOP) method in a rotating packed bed (RPB) under a higher initial aniline concentration of 0.5 M. The influence of oxidation times and ammonium peroxydisulfate (APS) dosages on the morphology, yield and conductive property of PANI were investigated, the products were characterized by SEM and UV–vis. Moreover, the anti-corrosion property and water dispersity of the as-prepared PANI nanofibers were also studied. The results showed that two-step oxidation process was an efficient way for mass production of PANI nanofibers by HGCOP, in which the optimum molar ratio of APS/aniline in the first and second oxidation stage was 0.5 and 0.25, respectively. PANI nanofibers with yield of 76.1%, diameters of 50–80 nm and average aspect ratio of 9.7 were obtained under the optimized condition. The PANI nanofibers were highly dispersible in water and exhibited an outstanding anti-corrosion effect, which could be applied to the environment-friendly processing and applications.     

多功能性聚苯胺/聚合物纳米复合材料的制备及应用

基于国内外最新研究文献及本课题组的研究,综述了多功能性聚苯胺/聚合物纳米复合材料的制备方法、性能及应用前景。聚苯胺/聚合物纳米复合材料可以由机械共混法、涂布法和原位聚合法,如分散聚合法、模板诱导聚合法及电化学聚合法制备得到。聚苯胺/聚合物纳米复合材料在透明导电塑料薄膜、防静电涂料、导电纤维、电致发光器件、电磁屏蔽材料等领域有着广阔的应用前景。     

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     

Facile fabrication of hollow polyaniline spheres and its application in supercapacitor

Polyaniline (PANI) is a promising electroactive material for pseudocapacitor due to the existence of the electronic conjugation structure. Here we demonstrate a novel approach to prepare hollow polyaniline nanospheres. In this process, uniform poly (methyl methacrylate- butyl methacrylate - methacrylic acid) (PMMA-PBMA-PMAA) latex microspheres as self-sacrificial templates were rapidly prepared through an emulsion polymerization method. Then the hollow PANI (H-PANI) nanospheres were obtained directly through an in-situ chemical oxidative polymerization of aniline in the presence of PMMA-PBMA-PMAA microspheres, which can be explained by the “dissolution” of templates and phase separation between the constituent polymers. The structure and morphology of the nanophase materials have been characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectra. The specific capacitance of H-PANI is 485.5 F g^?1 at 1 A g^?1 and there is 69% performance attenuation after 500 cycles, which show a promising electrochemical performance.     

电化学聚合过程中聚苯胺降解的研究

本文应用循环伏安法和紫外吸收光谱对苯胺电化学聚合过程中聚苯胺的降解进行了研究。结果表明，随着聚合的进行，产物聚苯胺同时发生一定程度降解。     

过硫酸盐氧化处理苯胺研究

苯胺是重要的化工原料,但其毒性很强。近年来因各种原因,很多地下水受到苯胺的污染。本研究针对此种情况,提出用过硫酸盐氧化技术处理苯胺污染,考察了溶液pH、反应温度等对苯胺降解的影响。     

Conducting polymers prepared by oxidative polymerization: polyaniline

Polyaniline (PANI) is one of the most intensively investigated polymers during the last decade. The establishment of the scientific principles allowing regulation of its properties, determining the potential application areas (alternative energy sources and transformers, media for erasable optical information storage, non-linear optics, membranes, etc.) is an important scientific problem. We have shown for the first time that the behavior of this polymer is subject to the same basic principles as the polymerization process itself. Both the polymerization of aniline and the subsequent transformations of polyaniline have to be regarded as typical redox processes, where the direction and establishment of equilibrium are dependent on the oxidation potentials and concentrations of the reactants (and also on pH of the medium, affecting the values of oxidation potential of the reactants). Such an approach allows us to identify the oxidative polymerization of aniline (and presumably of thiophene and pyrrole) as a new area in cationic polymerization, wherein the conditions of initiation, propagation and termination of the chains can be expressed by means of the electrochemical potential of the system. Furthermore, this allows an elucidation of the key problems related to the main types of transformations of this polymer (the so-called oxidative and non-oxidative doping of polyaniline). It also gave us a reason to suggest a novel original classification of the numerous potential application areas of PANI.     

Electrorheological characterization of semiconducting polyaniline suspension

Electrorheological (ER) properties of polyaniline suspensions in silicone oil with various experimental conditions were investigated. These suspensions exhibit dramatic changes in their rheological properties which are caused by the formation of particle chain structures induced by an applied electric field. Polyaniline was synthesized by the chemical oxidation of aniline with ammonium peroxysulfate. This study examined the effects of electric field, volume fraction, polymerization temperature and operation temperature on the ER properties of polyaniline suspensions in silicone oil. Rheological measurements were carried out by using a rotational rheometer with a high voltage generator in both controlled shear stress and shear rate modes. Experimental results showed that the ER properties were enhanced by increasing the volume fraction and electric field and were independent of the operating tempertures. The best ER properties were also obtained by using polyaniline particles synthesized at -10°C, and these had a conductivity of ? 10^?10 S/cm.