Protection of epoxy coatings containing polyaniline modified ultra-short glass fibers

Polyaniline (PANI) was covered on the surface of ultra-short glass fibers uniformly by in situ polymerization of aniline. Epoxy coatings with different contents of PANI ultra-short glass fibers and ultra-short glass fibers were formulated and their protection abilities were evaluated by means of open-circuit potential, electrochemical impedance spectroscopy and salt spray test. The results showed that the PANI ultra-short glass fibers had a significant inhibitive effect and its best volume fraction was10% in epoxy coating. XPS results indicated that a dense, stable passive oxide film of Fe₂O₃/Fe₃O₄ was formed on the steel surface beneath the coating.     

The mechanism of the oxidative polymerization of aniline and the formation of supramolecular polyaniline structures

Polyaniline is one of the most important conducting and responsive polymers. A molecular mechanism for the oxidation of aniline is proposed. This mechanism explains the specific features of aniline oligomerization and polymerization in various acidity ranges. The formation of polyaniline precipitates, colloids and thin films is reviewed and discussed on the basis of the chemistry of aniline oxidation. The generation of nanostructures, i.e. granules, nanotubes, nanowires and microspheres, is also considered. Oligomers containing phenazine constitutional units play an important role in self‐assembly to form templates. Polyaniline chains then grow from these templates and produce the various individual morphologies. Copyright © 2008 Society of Chemical Industry     

Doped polyaniline/multiwalled carbon nanotube composites: Preparation and characterization

Polyaniline (PANI)/multiwalled carbon nanotube (MWNT) composites with a uniform tubular structure were prepared from in situ polymerization by dissolving amino‐functionalized MWNT (a‐MWNT) in aniline monomer. For this the oxidized multiwalled nanotube was functionalized with ethylenediamine, which provided ethylenediamine functional group on the MWNT surface confirmed by Fourier‐transform infrared spectra (FT‐IR). The a‐MWNT was dissolved in aniline monomer, and the in situ polymerization of aniline in the presence of these well dispersed nanotubes yielded a novel tubular composite of carbon nanotube having an ordered uniform encapsulation of doped polyaniline. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanotubes were coated with a PANI layer. The thermal stability and electrical conductivity of the PANI /MWNTs composites were characterized by thermogravimetric analysis (TGA) and conventional four‐probe method respectively. Compared with pure PANI, the electrical conductivity and the decomposition temperature of the MWNTs/PANI composites increased with the enhancement of MWNT content in PANI matrix. POLYM. COMPOS., 34:1119–1125, 2013. © 2013 Society of Plastics Engineers     

Effect of β‐cyclodextrin on the solid‐state synthesized polyaniline doped with hydrochloric acid

Polyaniline (PANI) salts doped with hydrochloric acid were prepared by using solid‐state polymerization in the presence of β‐cyclodextrin (β‐CD) at room temperature. The fourier transform infrared (FTIR) spectra, ultraviolet‐visible absorption spectra, X‐ray diffraction patterns were used to characterize the molecular structures of these polymers. Cyclic voltammetry study and conductivity measurements were done to investigate their electrochemical behaviors. The morphology of polymers was studied by the scanning electron microscopy and transmission electron microscopy. The results showed that PANI salts prepared in the presence of β‐CD had different physicochemical characteristics compared with PANI salt prepared in the absence of β‐CD. When the molar ratio of aniline to β‐CD was 80/20, the obtained PANI salt displayed higher crystallinity, conductivity and electrochemical properties. However, these properties were opposite on condition that the molar ratio of aniline to β‐CD was 50/50. The results also revealed that the morphology of PANI salt was affected by β‐CD, especially at aniline/β‐CD molar ratio in the feed of 50/50, in which PANI salt displayed rodlike structure morphology with a diameter of near 80–100 nm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Electrochemical impedance study of polyaniline electrocoated porous carbon foam

Electropolymerization of aniline on mesophase pitch based carbon foam has been studied in order to evaluate the influence of conductive polymer coating on the properties of carbon foam. The surface morphology of the coating was determined by scanning electron microscopy (SEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical properties of resulting modified carbon foam samples. Polyaniline (PANI) electrocoated-mesophase pitch based carbon foam showed good capacitor behavior in 0.5 M H₂SO₄. Better capacitive behavior is obtained for 100 and 150 mV/s compared to other scan rates, under these faster scan rates thinner films of PANI coatings were combined with more porous structure of carbon foam. Conductivity of the carbon foam was increased from 9.23 to 13.73 S/cm by electrocoating of PANI.     

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.     

High dielectric constant polyaniline/epoxy composites via in situ polymerization for embedded capacitor applications

Polyaniline (PANI)/epoxy composites with different polyaniline (PANI) contents were successfully developed by in situ polymerization of aniline salt protonated with camphorsulfonic acid within epoxy matrices and fully characterized. The influence of PANI loading levels on various properties was also explored. Dielectric and electrical properties of PANI/epoxy composites were studied for samples in parallel plate configuration. A PANI/epoxy composite prepared in this fashion reached a high dielectric constant close to 3000, a dielectric loss tangent less than 0.5 at room temperature and 10 kHz. The hardener type was also found as a critical parameter for the dielectric properties of PANI/epoxy composites. The distribution of the conductive element clusters within the polymer matrix was studied by SEM and correlated to the dielectric behavior of the composite films.     

All electrochemical synthesis of polyaniline/silica sol–gel materials

A potentiostatic method has been employed to obtain silica layers on the surface of glassy carbon electrodes from a precursor sol–gel solution. The silica-modified electrodes were then used as a porous matrix for the electrochemical growth of conducting polyaniline. As a result, the overall synthesis of an organic–inorganic nanohybrid material has been achieved only by electrochemical methods. The growth of polyaniline is, in the first step, confined inside the silica matrix and appears to be controlled by the diffusion of aniline monomer units. Later, once the polyaniline fibers have reached enough length, emerge out of the template and the growth kinetics becomes comparable to that for polyaniline synthesized on a bare electrode. The silica matrix has a positive effect on the electrical capacitance of Pani since the polymer chains grow dispersed and the collapse between them is minimized.     

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。     

Enzymatic synthesis of colloidal polyaniline particles

Polyaniline colloidal particles were enzymatically synthesized in aqueous media using poly(vinyl alcohol) as steric stabilizer. Hydrochloric acid, toluenesulfonic acid, and camphorsulfonic acid were used as doping agents during polymerization. Polyaniline showed chemical redox reversibility as demonstrated by changes in its electronic absorption spectra. Fourier transform infrared and UV-visible spectroscopic studies indicate a linear chemical structure of the synthesized polymer, whereas the results from X-ray photoelectron spectroscopy indicate the adsorption of poly(vinyl alcohol) at the surface of the particles. The doping agent used during the enzymatic polymerization of aniline influenced morphology and thermal stability of the synthesized particles. Polyaniline colloids prepared using p-toluenesulfonic acid showed spherical morphology and a narrow size distribution as shown by scanning electron microscopy and dynamic light scattering.     

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。     

Recent progress in chemical modification of polyaniline

Polyaniline (PANI) has been the subject of considerable recent interest because of their unique electrical behavior, good environmental stability in doped and neutral states, ease of synthesis and wide applications in different fields. However, the main drawback of PANI is lack of solubility, which explains its limited processability due to a rigid backbone. Various procedures have been adapted to improve its processability. The major part of this review is a discussion of some of the methods employed for chemical modification of PANI, including doping via Acid–Base chemistry, sulfonation of PANI or copolymerization of aniline with sulfonated aniline derivatives, synthesis of PANI composites with processable polymers, copolymerization of aniline with substituted corresponding monomers, incorporation of polymeric chains or long and flexible alkyl chains in the PANI backbone, and enzymatic polymerization of aniline during the last decade.     

The unique morphology role of thorn surface in determining electrochemical performance of polyaniline nano‐fibers via one‐step method

Polyaniline nano‐fibers with thorn surface morphology (T‐PANI) were synthesized by one‐step polymerization with adding additional aniline at later stage of chemical oxidation synthesis. In order to investigate the morphology role in determining electrochemical performance, the nano‐fibers PANI without thorn (PANI) was synthesized by the same polymerization process but at different time to add additional aniline. Material structures were characterized by field emission scanning electron microscope and Brunauer‐Emmett‐Teller method, and electrochemical performance was tested through cyclic voltammograms, galvanostatic charge‐discharge and electrochemical impedance spectroscopy. The data showed that the specific capacitance of T‐PANI was 443 F g^?1 at 5 mA cm^?2, which was much more than that of PANI (338 F g^?1 at 5 mA cm^?2). The solution resistance, charge transfer resistance, and diffuse resistance of T‐PANI were also lower than these of PANI. The results indicate that the thorn surface structure plays an important role in determining the electrochemical performance of polyaniline, which attribute to the improvements in pore size, pore distribution, special surface area, and conductivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42266.     

Preparation and electrochemical properties of polyaniline/reduced graphene oxide composites

Polyaniline (PANI)/reduced graphene oxide (rGO) composites were synthesized by in situ oxidative polymerization of aniline on reduced graphene sheets. Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscopy were used to characterize the composites. The results indicated PANI/rGO composites were produced and contained covalent bonds between the functional groups of PANI and rGO. A uniform coating of PANI on the rGO sheets had a synergistic effect on the properties of the composites. The electrochemical properties of the PANI/rGO composites produced using different feed ratios of aniline to rGO were studied. The results showed that the composites exhibited a maximum specific capacitance of 797.5 F/g at 0.5 A/g and minimum charge transfer resistance of 0.98 Ω when the feed ratio of aniline to rGO was 2:1. These values were superior to those of pure PANI and rGO. The composites also displayed excellent cycling stability, with specific capacitance retention of 92.43% after 1000 cycles. These stable structural composites show promise for the development of new supercapacitor applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46103.     

The electrochemical deposition of polyaniline at pure aluminium: electrochemical activity and corrosion protection properties

Polyaniline films were electrodeposited at pure aluminium from a tosylic acid solution containing aniline. These polymer films exhibited similar characteristics as pure polyaniline electrosynthesized at an inert platinum electrode, when removed from their respective substrates and dissolved in NMP. Both polymers had similar molecular weights and similar UV-visible absorption spectra. However, the aluminium substrate had a considerable effect on the electrochemical activity of the films. The polyaniline films deposited at aluminium appeared to lose electroactivity and the electrochemical impedance data were governed by the oxidized aluminium substrate. This is consistent with a galvanic interaction between the polymer and the aluminium substrate, giving rise to oxidation of the aluminium and reduction of the polymer. The polyaniline deposits appeared to offer only a slight increase in the corrosion resistance of aluminium. Surface potential measurements, using a scanning vibrating probe, showed that attack initiated underneath the polymer under anodic polarization conditions, indicating that chloride anions diffuse across the polymer to react at the underlying aluminium substrate.     

Preparation of aqueous polyaniline dispersions by micellar‐aided polymerization

Polyaniline (PAn) dispersed in water was prepared with sodium dodecylsulfonate (SDS) as a surfactant with varying concentrations of aniline and HCl and molar ratios of SDS/aniline. The PAn dispersion was homogeneous and stable, and its pH value could be adjusted. The conductivity of PAn powder, precipitated from this dispersion, was as high as 20 S/cm. The transmission electron microscopy morphology of PAn assembled in the dispersion was particle‐like, fiber‐like, or coil‐like, depending on the initial concentration of SDS and aniline. The polymerization of aniline was accelerated by SDS, which was confirmed by open‐circuit potential measurement during the polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1550–1555, 2003     

Comparison of the growth process and electrochemical properties of polyaniline films prepared by pulse potentiostatic and potentiostatic method on titanium electrode

Polyaniline (PANI) films were deposited on titanium (Ti) electrode in a bath containing 0.3 mol L^?1 aniline and 1 mol L^?1 HNO₃ by pulse potentiostatic method (PPM) and potentiostatic method (PM). The chronoamperograms during aniline polymerization were recorded, and the morphologies of PANI films prepared with different polymerization periods were examined under scanning electron microscope. The difference between the processes of PANI films growth was studied. The growth processes of PANI films prepared by PPM and PM are divided into two stages. For both PPM and PM, the first stage corresponds to the formation of a compact granular PANI layer on the surface of Ti electrode. The second stage corresponds to further growth of PANI film on the surface of the compact granular PANI film. However, the PANI films prepared by PPM and PM show different morphologies in this stage. In addition, the electrochemical properties of the PANI films prepared by PPM and PM are obviously different. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 458–463, 2007     

Effects of polyaniline content in chlorrub‐based coatings on corrosion protection of steel

Corrosion protection of steel coated with chlorrub resin containing polyaniline has been studied in 3% NaCl by electrochemical impedance spectroscopy (EIS). Polyaniline was prepared by oxidative polymerization of aniline using ammonium persulphate in HCl medium. Using the synthesized polyaniline, paints were prepared using chlorrub resin with 1, 3, and 5% polyaniline. The variation of resistance and capacitance of the coating with time has been found out be EIS. The study has shown that the polyaniline content of 1% is able to offer sufficient protection of steel in neutral media and usage of higher percentage of polyaniline does not have beneficial effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3994–3999, 2006     

Preparation of conductive polyaniline/nylon‐6 composite films by polymerization of aniline in nylon‐6 matrix

Polyaniline (PANI)/Nylon‐6 composite films were prepared by oxidative polymerization of aniline (ANI) inside host Nylon‐6 film. Such a composite has the desired electro‐active and mechanical properties to serve as a self‐standing functional unit. Comparative studies on sorption of ANI by Nylon‐6 matrix from various ANI containing media were conducted revealing superior ANI uptake from neutral ANI solution in water. ANI content was measured to be as high as 12%. Spectroscopic measurements showed that hydrogen bonding seemed to play important role in ANI sorption by Nylon‐6 matrix. Polymerization was monitored using atomic force microscopy and conductivity measurements. The morphology studies showed the appearance of PANI nanodomains on Nylon‐6 surface in the early stages of the polymerization. Eventually the domains coalesced during polymerization forming a continuous PANI layer. The conductivity measurements confirmed the change of the morphology from isolated islands to continuous conducting surface by drastic increase in conductivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009