Electrochemical Behavior of Polyaniline,Poly(o-Anisidine) and Their Copolymer Thin Films in Inorganic and Organic Supporting Electrolytes

Abstract

The influence of inorganic and organic supporting electrolytes on electrochemical, optical, and conducting properties of polyaniline, poly(o-anisidine), and poly(aniline-co-o-anisidine) thin films were investigated. Homo- and copolymer thin films were synthesized electrochemically, under cyclic voltammetric conditions in aqueous solutions of inorganic acids, viz., H₂SO₄, HCl, HNO₃, H₃PO₄, and HClO₄ and organic acids, viz., benzoic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid, and adipic acid, at room temperature. The films were characterized by cyclic voltammetry, ultraviolet (UV)–Visible spectroscopy, and conductivity measurements using four probe technique. The optical absorption spectra indicated that the formation of the conducting emeraldine salt (ES) phase took place in all the inorganic supporting electrolytes used whereas, inorganic supporting electrolytes ES phase formed only with oxalic acid. It was also observed that the current density and conductivity of thin films are greatly affected by the nature and size of the anion present in the electrolyte. The formation of copolymer has also been confirmed by differential scanning calorimetry.     

Glucose oxidase electrodes of poly(o‐anisidine), poly(o‐toluidine), and their copolymer as biosensors: A comparative study

Thin films of poly(o‐anisidine) (POA), poly(o‐toluidine) (POT), and their copolymer poly(o‐anisidine‐co‐o‐toluidine) (POA‐co‐POT) were electropolymerized in solutions containing 0.1M monomer(s) and 1M H₂SO₄ as an electrolyte through the application of a sequential linear potential scanning rate of 50 mV/s between ?0.2 and 1.0 V versus an Ag/AgCl electrode on a platinum electrode. A simple technique was used to construct glucose sensors through the entrapment of glucose oxidase (GOD) in thin films of POA, POT, and their copolymer POA‐co‐POT, which were electrochemically deposited on a platinum plate in phosphate and acetate buffers. The maximum current response was observed for POA, POT, and POA‐co‐POT GOD electrodes at pH 5.5 and at a potential of 0.60 V (vs Ag/AgCl). The phosphate buffer yielded a fast response in comparison with the acetate buffer in amperometric measurements. The POT GOD electrode showed a fast response and was followed by POA‐co‐POT and POA GOD electrodes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1877–1884, 2004     

Synthesis,characterization, and comparison of self‐doped,doped, and undoped forms of polyaniline,poly(o‐anisidine), and poly[aniline‐co‐(o‐anisidine)]

Polyaniline (PANI), poly(o‐anisidine), and poly[aniline‐co‐(o‐anisidine)] were synthesized by chemical oxidative polymerization with ammonium persulfate as an oxidizing reagent in an HCl medium. The viscosities, electrical conductivity, and crystallinity of the resulting polymers (self‐doped forms) were compared with those of the doped and undoped forms. The self‐doped, doped, and undoped forms of these polymers were characterized with infrared spectroscopy, ultraviolet–visible spectroscopy, and a four‐point‐probe conductivity method. X‐ray diffraction characterization revealed the crystalline nature of the polymers. The observed decrease in the conductivity of the copolymer and poly(o‐anisidine) with respect to PANI was attributed to the incorporation of the methoxy moieties into the PANI chain. The homopolymers attained conductivity in the range of 3.97 × 10^?3 to 7.8 S/cm after doping with HCl. The conductivity of the undoped forms of the poly[aniline‐co‐(o‐anisidine)] and poly(o‐anisidine) was observed to be lower than 10^?5 J/S cm^?1. The conductivity of the studied polymer forms decreased by the doping process in the following order: self‐doped → doped → undoped. The conductivity of the studied polymers decreased by the monomer species in the following order: PANI → poly[aniline‐co‐(o‐anisidine)] → poly(o‐anisidine). All the polymer samples were largely amorphous, but with the attachment of the pendant groups of anisidine to the polymer system, the crystallinity region increased. The undoped form of poly[aniline‐co‐(o‐anisidine)] had good solubility in common organic solvents, whereas doped poly[aniline‐co‐(o‐anisidine)] was moderately crystalline and exhibited higher conductivity than the anisidine homopolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis and characterization of conducting copolymers from aniline and o‐anisidine in HCl solutions

Conducting poly(aniline‐co‐o‐anisidine) (PAS) films with different ratios of aniline units in the polymer chain were prepared by oxidative polymerization of different molar ratios of aniline and o‐anisidine in 1 M HCl using cyclic voltammetry. Due to the much higher reactivity of o‐anisidine, the structure and properties of PASs were found to be dominated by the o‐anisidine units. The polymerization of poly‐o‐anisidine and PASs followed zero‐order kinetics with respect to formation of the polymer (film thickness) and the autocatalytic polymerization of aniline was completely inhibited. In contrast to polyaniline, a decrease in the polymerization temperature was found to increase the amount of copolymer formed and its redox charge. The presence of aniline units in PASs led to a pronounced increase in the molecular weight and conductivity, and a decrease in the solubility in organic solvents. Repetitive charging/discharging cycles showed that PASs resist degradation more than polyaniline. Copyright © 2003 Society of Chemical Industry     

Synthesis and characterization of poly(o‐anisidine)/V2O5 and poly(o‐anthranilic acid)/V2O5 nanocomposites

Poly(o‐anisidine)/V₂O₅ and poly(o‐anthranilic acid)/V₂O₅ nanocomposites were prepared by in situ intercalative polymerization, and the structure and electrical properties of these nanocomposites were investigated using GPC, TGA, XRD, TEM, FTIR, UV‐vis as well as conductivity measurement. The results show that the steric effect and nature of the substituting groups in the aromatic ring has an influence on the structure and electrical properties of the nanocomposites. Poly(o‐anisidine) or poly(o‐anthranilic acid) exists as a monolayer of outstretched chains in the gallery of the V₂O₅ xerogel owing to the confined environment in the nanometer‐size gallery. And intercalation of poly(o‐anisidine) or poly(o‐anthranilic acid) can improve the conductivity of V₂O₅ xerogel. Copyright © 2005 Society of Chemical Industry     

Synthesis of poly(aniline‐co‐o‐toluidine) coatings and their corrosion‐protection performance on low‐carbon steel

Strongly adherent poly(aniline‐co‐o‐toluidine) coatings were synthesized on low‐carbon‐steel substrates by the electrochemical copolymerization of aniline with o‐toluidine with sodium tartrate as the supporting electrolyte. These coatings were characterized with cyclic voltammetry, ultraviolet–visible absorption spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and scanning electron microscopy. The formation of the copolymer with the mixture of monomers in the aqueous sodium tartrate solution was ascertained by a critical comparison of the results obtained from the polymerizations of the individual monomers, aniline and o‐toluidine. The optical absorption spectrum of the copolymer was drastically different from the spectra of the respective homopolymers, polyaniline and poly(o‐toluidine). The extent of the corrosion protection offered by poly(aniline‐co‐o‐toluidine) coatings to low‐carbon steel was investigated in aqueous 3% NaCl solutions by open‐circuit‐potential measurements and a potentiodynamic polarization technique. The results of the potentiodynamic polarization measurements showed that the poly(aniline‐co‐o‐toluidine) coatings provided more effective corrosion protection to low‐carbon steel than the respective homopolymers. The corrosion rate depended on the feed ratio of o‐toluidine used for the synthesis of the copolymer coatings. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:1868–1878, 2007     

Electrochemical preparation of poly(o‐toluidine) film and its application as a permselective membrane

Poly(o‐toluidine) films were electrochemically synthesized on Pt electrodes at a constant potential (0.75 V versus Ag/AgCl) from a deoxygenated aqueous solution of 0.1M toluidine dissolved in 0.1M KCl. To form permselective polymeric film electrodes, poly(o‐toluidine) films at different thicknesses were prepared by varying the amount of charge consumed during electrochemical polymerization. Then, experimental parameters (e.g., concentrations of monomer and electrolyte and pH of the phosphate buffer salt solution) affecting the polymeric film thickness were optimized. Permeation of the various electroactive and nonelectroactive species such as ascorbic acid, oxalic acid, hydrogen peroxide, lactose, sucrose, and urea through the optimized poly(o‐toluidine)‐coated electrodes was investigated using a chronoamperometric technique. From experimental results, it was found that a poly(o‐toluidine)‐coated electrode permitted the oxidation of hydrogen peroxide and prevented the permeation of the mentioned electroactive and nonelectroactive species. In other words, it was seen that this polymeric electrode responded to only hydrogen peroxide selectively. Thus, it has been claimed that a poly(o‐toluidine)‐coated Pt electrode can be used as a permselective polymeric membrane to overcome interference problems occurring in the hydrogen peroxide‐based biosensor applications. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2141–2146, 1999     

Copolymers of aniline with o‐ and m‐toluidine: synthesis and characterization

Copolymers of aniline and toluidine were synthesized by oxidative chemical polymerization using different ratios of the monomers in the feed, and characterized by a number of techniques including UV–visible, IR, Raman, ¹H NMR and EPR spectroscopies, as well as by thermogravimetric analysis and conductivity measurements. The properties of the copolymers are influenced by the amount of toluidine in the copolymer. Poly(o‐toluidine) and poly(m‐toluidine) are noticeably different in their solubility and conductivity. The copolymers show better solubilities than polyaniline but have lower conductivities. Differences in the properties of the salt and base forms of the copolymers are pointed out. Copyright © 2003 Society of Chemical Industry     

Studies on the dielectric properties of poly(o‐toluidine) and poly(o‐toluidine‐aniline) copolymer

Poly(o‐toluidine) (PoT) and poly(o‐toluidine co aniline) were prepared by using ammonium persulfate initiator, in the presence of 1M HCl. It was dried under different conditions: room temperature drying (48 h), oven drying (at 50°C for 12 h), or vacuum drying (under vacuum, at room temperature for 16 h). The dielectric properties, such as dielectric loss, conductivity, dielectric constant, dielectric heating coefficient, loss tangent, etc., were studied at microwave frequencies. A cavity perturbation technique was used for the study. The dielectric properties were found to be related to the frequency and drying conditions. Also, the copolymer showed better properties compared to PoT alone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 592–598, 2004     

Comparison of poly(o‐anisidine) and poly(o‐anisidine‐co‐aniline) copolymer synthesized by chemical oxidative method

In this study, poly(o‐anisidine) [POA], poly(o‐anisidine‐co‐aniline) [POA‐co‐A], and polyaniline [PANi] were chemically synthesized using a single polymerization process with aniline and o‐anisidine as the respective monomers. During the polymerization process, p‐toluene sulfonic acid monohydrate was used as a dopant while ammonium persulfate was used as an oxidant. N‐methyl‐pyrolidone (NMP) was used as a solvent. We observed that the ATR spectra of POA‐co‐A showed features similar to those of PANi and POA as well as additional ones. POA‐co‐A also achieved broader and more extended UV–vis absorption than POA but less than PANi. The chemical and electronic structure of the product of polymerization was studied using Attenuated Total Reflectance spectroscopy (ATR) and UV–visible spectroscopy (UV–vis). The transition temperature of the homopolymers and copolymers was studied using differential scanning calorimetry and the viscosity average molecular weight was studied by using dilute solution viscometry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Copolymerization of poly(1‐naphthylamine) with aniline and o‐toluidine

The commercial use of polyaniline has been impeded by its intractable nature and insolubility. The use of substituted polyaniline has been attempted mainly to increase the processibility of polyaniline, but this approach usually results in the lowering of the conductivity. This study reports the synthesis of poly(1‐naphthylamine), a fused ring derivative of polyaniline, and its copolymers with aniline and o‐toluidine via a chemical polymerization method. Spectral, thermal, morphological, and conductivity studies were carried out to elucidate the influence of the incorporation of aniline and o‐toluidine units into poly(1‐naphthylamine). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chemical grafting of aniline and o‐toluidine onto poly(ethylene terephthalate) fiber

Graft copolymerization of poly(aniline) and poly(o‐toluidine) onto poly(ethylene terephthalate) fiber was conducted by using peroxydisulfate as a lone initiator under nitrogen atmosphere at various experimental conditions in aqueous hydrochloric acid medium. The grafting of poly(aniline) and poly(o‐toluidine) onto poly(ethylene terephthalate) fiber was verified by recording cyclic voltammetry of the grafted fiber, conductivity measurements, and thermal analysis. Graft parameters—such as % grafting, % efficiency, and the rate of grafting—were followed. Grafting was always accompanied by homopolymerization. The rate of homopolymerization was also followed in all experimental conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 121–128, 1999     

Melt processable conducting poly(aniline‐co‐o‐anisidine)/linear low‐density polyethylene composites with ethylene‐acrylic acid copolymer as compatibilizer

Conducting composites of aniline/o‐anisidine copolymer doped by dodecylbenzenesulfonic acid (P(An‐co‐oAs)‐DBSA), linear low‐density polyethylene (LLDPE), and ethylene–acrylic acid copolymer (EAA) as compatibilizer were prepared by melt processing. The effects of composition on electrical conductivity, resistivity‐temperature characteristic, and mechanical properties were also investigated. The electrical conductivity of ternary composites markedly increased due to compatibilizition and protonation effect of the EAA. The SEM micrograph shows that the compatibility between the P(An‐co‐oAs)‐DBSA and the LLDPE matrix is enhanced after the introduction of EAA. The positive temperature coefficient of resistivity characteristic is observed. Tensile strength of P(An‐co‐oAs)‐DBSA/LLDPE/EAA composites is improved, compared with P(An‐co‐oAs)‐DBSA/LLDPE composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1511–1516, 2005     

Synthesis and characterization of aniline and o‐toluidine conducting copolymer microtubes with the template‐synthesis method

Copolymer microtubes composed of aniline and o‐toluidine were prepared through the synthesis of the desired polymer within the pores of a microporous anodic aluminum oxide (AAO) template. Scanning electron microscopy and transmission electron microscopy revealed that the obtained copolymer microtubes had uniform and well‐aligned arrays, and the aspect ratios of the AAO membranes could be controlled through their diameter and length. Infrared spectrometry and X‐ray photoelectron spectroscopy supported the surface analysis for the microtubes and also proved the formation of copolymers. Ultraviolet–visible/near‐infrared spectra proved that the doping effect decreased with an increase of o‐toluidine in the copolymers, but the solubility greatly improved (up to 3.83 g/L in N,N‐dimethylformamide), and the conductivity was as high as approximately 17.4 S cm^?1. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1539–1543, 2005     

Synthesis of poly(o‐toluidine) in the presence of magnetic field and dysprosium chloride

The poly‐o‐toluidine (POT) was prepared under different magnetization in solution containing 0.5 mol dm^?3o‐toluidine, 1.0 mol dm^?3 HCl with and without 0.5 mol dm^?3 DyCl₃, respectively. Their conductivity, UV–vis, FTIR spectra, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) were investigated. The results of conductivity showed that magnetic field and the cooperative effect of Dy³⁺ and magnetic field do obvious effect to conductivity of POT. Meantime, they also can make the energy for the π–π* transitions and quinoid ring transition in UV–vis spectra smaller. At high magnetization the peaks of POT due to Q? NH⁺? B or B? NH⁺? B and C? H out of plane on 1,4‐ring or 1,2,4‐ring disappeared in FTIR spectra. Magnetic field and Dy³⁺ can make three dimensions morphologies of the POT clear, but they scarcely affect the crystallinity of POT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2174–2179, 2007     

Towards enhanced electrochemical capacitance with self‐assembled synthesis of poly(pyrrole‐co‐o‐toluidine) nanoparticles

Poly(pyrrole‐co‐o‐toluidine) (PPOT) nanoparticles for electrochemical capacitors are easily and productively synthesized by a chemical oxidative polymerization of pyrrole (PY) and o‐toluidine (OT) in 0.5M HCl without any external additive. The polymerization yield, electrical conductivity, and size of the copolymer nanoparticles can significantly be optimized by the oxidant/monomer molar ratio and polymerization temperature. The chemical structure of the obtained copolymer is characterized by UV–vis and FTIR. The copolymer nanoparticles synthesized at 10°C are found to generally have irregular granular morphology with a diameter of 60–100 nm and a small polydispersity index of 1.06 by laser particle‐size analyzer, FE‐SEM, and TEM, and good dispersibility in water. The formation mechanism of the nanoparticles is proposed based on the powerful amphipathicity from comonomer aggregate formed by PY and OT in the monomer solution. The PPOT nanoparticles possess a specific capacitance of 310 F g^?1 at 25 mV s^?1 as well as retain 81% of the initial specific capacitance value after 1000 cycles, while its energy density and power density are found to be 40.2 and 1196 W Kg^?1 at 2 A g^?1. The enhanced electrochemical properties can be attributed to the nanostructural advantage of the PPOT. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42995.     

Electrochemical synthesis of poly(2‐iodoaniline) and poly(aniline‐co‐2‐iodoaniline) in acetonitrile

Poly(2‐iodoaniline) (PIANI) and poly(aniline‐co‐2‐iodoaniline) [P(An‐co‐2‐IAn)] were synthesized by electrochemical methods in acetonitrile solution containing tetrabutylammonium perchlorate (TBAP) and perchloric acid (HClO₄). The voltametry of the copolymer shows characteristics similar to those of conventional polyaniline (PANI), and it exhibits higher dry electrical conductivity than PIANI and lower than PANI. The observed decrease in the conductivity of the copolymer relative to PANI is attributed to the incorporation of the iodine moieties into the PANI chain. The structure and properties of these conducting films were characterized by FTIR and UV‐Vis spectroscopy and by an electrochemical method (cyclic voltametry). Conductivity values, FTIR and UV‐Vis spectra of the PIANI and copolymer were compared with those of PANI and the relative solubility of the PIANI and the copolymer powders was determined in various organic solvents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1652–1658, 2003     

Thermal and flame‐retardant properties of polyester fabric grafted with polyanilines

The chemical grafting of polyaniline, poly(o‐anisidine), and poly(o‐toluidine) on polyester fabric was carried out with ammonium peroxodisulfate in an acidic medium. The formation of the grafted fabric substrate was confirmed with reflectance spectroscopy, Fourier transform infrared spectroscopy, weight‐loss studies, and conductivity measurements. The grafting percentage and efficiency percentage were determined for the different grafted substrates. The thermal and flame‐retardant properties of these grafted substrates were elucidated. Thermogravimetric analysis thermograms and derivative thermogravimetry curves showed that the grafted substrates had a higher thermal stability and char‐residue percentage at 700°C. The grafted substrates showed a higher activation energy of thermal decomposition than the nongrafted substrates. The grafted substrates showed good flame retardancy, which was evident from the increase in the limited oxygen index in comparison with that of the nongrafted substrate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1981–1988, 2004     

Studies of solvent effect on the conductivity of 2‐mercaptopyridine‐doped solid polymer blend electrolytes and its application in dye‐sensitized solar cells

Solvents and electrolytes play an important role in the fabrication of dye‐sensitized solar cells (DSSCs). We have studied the poly(ethylene oxide)‐poly(methyl methacrylate)‐KI‐I₂ (PEO‐PMMA‐KI‐I₂) polymer blend electrolytes prepared with different wt % of the 2‐mercaptopyridine by solution casting method. The polymer electrolyte films were characterized by the FTIR, X‐ray diffraction, electrochemical impedance and dielectric studies. FTIR spectra revealed complex formation between the PEO‐PMMA‐KI‐I₂ and 2‐mercaptopyrindine. Ionic conductivity data revealed that 30% 2‐mercaptopyridine‐doped PEO‐PMMA‐KI‐I₂ electrolyte can show higher conductivity (1.55 × 10^?5 S cm^?1) than the other compositions (20, 40, and 50%). The effect of solvent on the conductivity and dielectric of solid polymer electrolytes was studied for the best composition (30% 2‐mercaptopyridine‐doped PEO‐PMMA‐KI‐I₂) electrolyte using various organic solvents such as acetonitrile, N,N‐dimethylformamide, 2‐butanone, chlorobenzene, dimethylsulfoxide, and isopropanol. We found that ac‐conductivity and dielectric constant are higher for the polymer electrolytes processed from N,N‐dimethylformamide. This observation revealed that the conductivity of the solid polymer electrolytes is dependent on the solvent used for processing and the dielectric constant of the film. The photo‐conversion efficiency of dye‐sensitized solar cells fabricated using the optimized polymer electrolytes was 3.0% under an illumination of 100 mW cm^?2. The study suggests that N,N‐dimethylformamide is a good solvent for the polymer electrolyte processing due to higher ac‐conductivity beneficial for the electrochemical device applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42489.     

Electrochemical synthesis and corrosion performance of poly(pyrrole-co-o-anisidine)

The electrochemical synthesis of poly(o-anisidine) homopolymer and its copolymerization with pyrrole have been investigated on mild steel. The copolymer films have been synthesized from aqueous oxalic acid solutions containing different ratios of monomer concentrations: pyrrole:o-anisidine, 9:1, 8:2, 6:4, 1:1. The characterization of polymer films were achieved with FT-IR, UV–visible spectroscopy and cyclic voltammetry techniques. The electrochemical synthesis of homogeneous-stable poly(o-anisidine) film with desired thickness was very difficult on steel surface. Therefore its copolymer with pyrrole has been studied to obtain a polymer film, which could be synthesized easily and posses the good physical–chemical properties of anisidine. The kinetics and rate of copolymer film growth were strongly related to monomer feed ratio. The introduction of pyrrole unit into synthesis solution increased the rate of polymerization and the substrate surface became covered with polymer film soon, while this process required longer periods in single o-anisidine containing solution. The protective behavior of coatings has been investigated against steel corrosion in 3.5% NaCl solution. For this aim electrochemical impedance spectroscopy (EIS) and anodic polarization curves were utilized. The synthesized poly(o-anisidine) coating exhibited significant protection efficiency against mild steel corrosion. It was shown that 6:4 ratio of pyrrole and anisidine solution gave the most stable and corrosion protective copolymer coating.