Synthesis of polyaniline in organic solvents

Effect of crown ethers on synthesis of polyaniline and its electrochemical behaviour in organic solvents

Polyaniline (PANI) is generally prepared in a water medium. However, a new method for the synthesis of PANI in an organic solvent was developed in this study. PANI was successfully synthesized in an organic cholesteric liquid crystal (CLC) matrix using ammonium peroxodisulfate and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as two initiators to progress the polymerization. Polymerization in the CLC matrix resulted to PANI with an ordered structure due to secondary doping in the monomer propagation process.

In this study, the optical active polyaniline film was examined with optical rotatory dispersion (ORD) through change in potential with spectroelectrochemical method. Polyaniline is one of the representative conducting polymers. Preparation of polyaniline is convenient because synthesis of polyaniline can perform in water medium. Conducting polymers shows electrochromism via change in the electronic state upon electrochemical redox process. Polyaniline forms various electronic states such as emeraldine base, emeraldine salt, and pernigraniline. This change allows to color tuning through electrochemical method. Further, optically active polyanilines have been synthesized in the presence of (+) or (-)-camphorsulfonic acid (CSA) by electrochemical polymerization or chemical polymerization with ammonium persulfate (oxidizing agent). Both electrochemical method and chemical method produce polyaniline through radical polymerization process. Polyaniline emeraldine salt as prepared form of polyaniline is doped with CSA, showing optical activity in the circular dichroism. In this research, we carried out to synthesis of polyaniline in the presence of optically active CSA, according to previously reported method (by Wallace et al). Here, we have found that the polyaniline thus prepared showed optically active electrochromism via electrochemical redox process in circular dichroism spectroscopy measurements. In our previous study, we calculated the ORD spectra for the polymer by Kramars - Kronich (K-K) conversion from circular dichromism. In the present research, we successfully obtained experimental data of optical rotation-spectroelectrochemical result, as a first example of optical rotation control of natural optical activity for conjugated polymers based on electrochemical method. In the case of low potential for the polymer in the electrochemical redox process, the polymer shows intense optical rotation at visible wavelength range. On the other hands, higher potential at around 1 V affords to give doping process for the polymer, resulting generation of polaron as charge carrier, which shows optical activity at near infrared region. We referred this optical charge carrier as “chiral charge carrier chiralions”. The electrochemical oxidation equivalents to electrochemical doping from the polymer. In other words, electrochemical oxidation gives electrochemical doping which results change in degree of optical rotation for the polymer. The control of optical ration for materials can be driven by magnetic field (Faraday rotation), and electric field (Kerr rotation). We propose a new phenomenon as ‘‘electrochemical optical rotation’’. The electro-conductivity of the polymer is measured with four-probe method. The polymer which is electronic doped state with (+)-CSA as electric dopant for production of radical cation (polarons) or dication (bipolarons) as charge carriers and chiral inducer for twisting main-chain. The polymer film was synthesized as followed. First, electrochemical polymerization of aniline as a monomer was carried out in excessive optically active (+)-CSA with three electrode system consisting of working electrode (indium-tin oxide coated glass), counter electrode (platinum wire), and reference electrode (SCE) in water. The polymerization reaction is rapidly progressed with formation of polymer thin film onto the counter electrode. The polymer was washed with excess amount of water, acetone. The electroactive polymer film was thus deposited on the electrode was used for optical activity measurements. Cyclic voltammetry (CV) measurements were carried out for the resultant polymer (monomer free) deposited on to the ITO coated glass electrode. The CV results with change in scan rate from 10-100 mV/s indicates electroactive. Increase of scan rate increases current density for the polymer due to increase of diffusion of ion in the electrolyte solution. Oxidation signals of the polymer are observed due to change in electronic state of the polymer. Corresponding reduction signals against oxidation process are observed, indicating reversible redox activity for the polymer. ORD measurement reveled that the polymer film thus obtained is optically active. The polyaniline can be formed helical structure due to doping of optically active CSA. We carried out in-situ ORD measurement with potential change, evaluating electrochemical driven change in optical rotation. Chemical structure of the double layer polymer is examined with Fourie transform infrared optical absorption spectroscopy measurements which reveled this polymer is polyaniline, and CSA as a dopant. Ultra-violet optical absorption measurements for the polymer film indicates intense and wide range absorptions from invisible to infrared range as charge carriers the delocalized along the main-chain, indicating the polymers are conductive materials. The advantages of the polymer film are formation of self-standing redox activity, tuning of optical activity and color coordination. This paper reports novel function of control optical rotation with electrochemical method examined with spectroelectrochemistry. This concept can be a first example as optical rotation effect of electro-optically active conducting polymers. This paper reports the charge carries of helical polyaniline as chiralions can tune via electrochemical method.

Improved Electrorheological Effect in Polyaniline Nanocomposite Suspensions

New hole-transporting pendant polymers with high glass- transition temperatures (Tgs) above 200 oC were designed and synthesized. Multilayer organic electrolu minescent (EL) devices using the new polymers as the hole-transport layer and quinacridone-doped tris(8-quinolinolato)aluminum as the emitting layer exhibited high performance. One of the hole-transporting polymers functioned well as a hole injection buffer layer in organic EL devices. New green- and orange-emitting penda nt polymers with high Tgs and desired ambipolar character were also designed and synthesized. Organic EL devices using these emitting polymers also exhibited good performance. One of the hole-transporting polymer showed a high hole carrier mobility of over 10 i 3 cm 2 V i 1 s i 1 at an electric field of 1.0 × 10 5 Vcm i 1 , as determined by a time-of-flight method. Keywords : non-conjugated pendant polymers, hole-transpor ting polymers, emitting polymers, hole-injection buffer layer, hole-transport layer, hole drift mobility 1. INTRODUCTION S -Conjugated polymers have received a great deal of attention as materials for electronics and optoelectronics, and have been the subject of recent extensive studies. On the other hand, non-conjugated polymers containing pendant S -electron systems generally have the following characteristic features; a variety of S -electron systems with various functions for pendant groups, chemical stability, solubility in organic solvents, processability such as film-forming capability, and the invariance of oxidation and reduction potentials irrespective of the doping degree. We have performed a series of studies on non-conjugated polymers containing pendant S -electron systems in the light of the consideration that such polymers also constitute a new class of photo- and electroactive materials for electronic, optoelectronic, and photonic devices, permitting the formation of large-area homogeneous films with mechanical strength by wet processes. We have developed several classes of photo-and electroactive pendant polymers. They include electrically conducting polymers, which have found applications as electrode materials for secondary

Photoluminescence (PL) of nonconjugated polymers brings a favorable opportunity for low-cost and nontoxic luminescent materials, while most of them still exhibit relatively weak emission. Strong PL from poly[(maleic anhydride)-alt-(vinyl acetate)] (PMV) from low-cost monomer has been found in organic solvents, yet the necessity of noxious solvents would hinder its practical applications. Herein, through a novel, eco-friendly, and one-step route, PMV-derived PL polymers can be fabricated with the highest quantum yield of 87% among water-soluble nonconjugated PL polymers ever reported. These PMV-derived polymers emit strong blue emission in both solutions and solids, and can be transformed into red-emission agents easily. These PL polymers exhibit application potentials in light-conversion agricultural films. It is assumed that this work not only puts forward a convenient preparation routine for nonconjugated polymers with high PL, but also provides an industrial application possibility for them.

Synthesis of polyaniline by use of the Ullmann reaction

This work reports a simple and effective method to prepare polyaniline (PANI) nanotubes with rectangular or circular cross section and hollow microspheres by using basic amino acids L‐lysine or L‐arginine as dopants and pH buffer agents, respectively. The research reveals that the pH value of the reaction solution at the beginning stage is a crucial factor to form PANI microstructures. The L‐lysine and L‐arginine have isoelectric point 9.74 and 10.76, which can maintain reaction solution at high pH value at the beginning reaction and assist aniline to couple in ortho‐position forming phenazine unit in the oligomer chain. The oligomer produces rectangular nanorods or microspheres by interaction. These oligomer microstructures act as templates for further polymerization to form PANI rectangular nanotubes and hollow microspheres. Decreasing the concentration of the basic amino acid or using acidic amino acid, the round nanotubes are formed. This method provides a simple route to prepare PANI microstructures with different morphologies without any foreign template or surfactant, and raises a new view on the polymerization process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Supramolecular polymers in water and non-polar solvents are extensively studied as model systems to mimic biological processes and as functional materials, respectively. The molecular designs to obtain supramolecular polymers in non-polar and polar solvents are typically orthogonal. Here we disclose a molecular design in which we combine hydrogen-bonding amide units attached to alkyl chains for compatibility with non-polar solvents and heteroatom in the π-conjugated core for interaction with polar solvents, leading to supramolecular polymerization of the same monomeric unit in both non-polar and mixture of polar solvents. Redox-active phenazine appended with two amide groups was studied as a model monomeric unit and it undergoes cooperative polymerization via intermolecular hydrogen-bonding resulting in one-dimensional(1D) nanostructures with co-facialtype packing in non-polar solvents. Whereas, in a mixture of polar solvents, a J-type packing was observed with tunable morphology from globular to 1D nanostructures based on the polarity of the cosolvent used. Further, solvent isotopic substitution studies suggest that the amphiphilicity of the system can be attributed to the nitrogen-atom in phenazine, which is capable of interacting with polar solvent molecules. Thus, this study opens up azaacenes as a new class of π-conjugated units for functional supramolecular polymers.

The current paper aims to study on synthesis of polyaniline (PANI)-polypyrrole (PPY) composite through simple interfacial polymerization method using chloroform as organic solvent, ammonium persulphate as an oxidant agent and sulphuric acid as a dopant. The composite was characterized by using Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and four pint probe methods. FESEM results showed the formation of fibrous PANI-PPY composite. FTIR and XRD results confirmed the successful formation of PANI-PPY composite. Four-point probe results showed the low electrical conductivity of the product. This study gives the better understanding on synthesis and characterization of the PANI-PPY through simple interfacial polymerization method.

Oxidative polymerization of aniline using the H2O2‐FeSO4 system gave polyaniline under mild conditions. The prepared powdery emeraldine base, a form of polyaniline, is blue black and shows high solubility in organic solvents (e.g., ca. 200 mg/mL in N‐methylpyrrolidone). The number‐average molecular weight (Mn) of the polymer obtained was 1,3–1,7 · 104 (via gel permeation chromatography vs. polystyrene) and Mw/Mn = 1,6–2,2. Poly(2‐ethylaniline) and poly‐(2‐propylaniline) with high molecular weights were also synthesized by this procedure in high yield.

We report the preparation of polyaniline (PAni) nanofibers by in situ intercalative polymerization of anilinium salt absorbed onto the nanoclay layers and modification of bentonite to an efficient nanohybrid gas sensor. The nanohybrid exhibited stable dispersion in different organic solvents like tetrahydrofuran, dimethyl acetamide and dimethyl sulphoxide. The Fourier transform infrared (FTIR) spectroscopic analysis indicated the formation of the benzenoid-quinoid structure of PAni in the nanohybrid. The wide angle X-ray diffraction study confirmed the crystallinity of the PAni nanofibers and the increase of d-spacing of the clay gallery on formation of the nanohybrid. The formation of the PAni nanofibers within the porous nanoclay layer was confirmed by the field-emission scanning electron microscopy. The sensitivity of the nanohybrid-based gas sensor towards toxic gases viz., acetone, benzene, ethanol and toluene was investigated. The nanohybrid gas sensor exhibited a high sensitivity to acetone compared to benzene, ethanol and toluene using ruthenium electrode than the silver electrode. Therefore, the prepared nanohybrid has the potential to be used as a promising gas sensor for the detection of toxic gases.

Comparison of electrical conductivity data obtained by four-electrode and four-point probe methods for graphite-based polymer composites

Capacitive type humidity sensor based on PANI decorated Cu–ZnS porous microspheres

Synthesis and characterization of polyaniline doped with polyvinyl alcohol by inverse emulsion polymerization