Emeraldine Form Of Polyaniline Research Articles

PANI/CFO@CNTs ternary composite system for EMI shielding applications

With the advancement of modern communication technologies and the internet of things (IoT), the manufacturing of light, flexible, and high-performance electromagnetic interference (EMI) shields is imperative to minimize harmful effects of radiation on humans and electronic devices. Lightweight ferrites/carbon allotropes/polymer-based ternary composites with abundant interfaces are potential candidates for excellent absorption materials due to their high attenuation capability and impedance matching. We report EMI shielding properties of composites made of carbon nanotubes (CNTs) decorated with cobalt ferrite (CFO) nanoparticles and coated with polyaniline (PANI). The electromagnetic properties of the CFO@CNTs binary composite have been fine-tuned by varying the weight percentage of CNTs. The formation of CFO, CNTs and emeraldine form of PANI was confirmed by XRD and Raman spectroscopy. Transmission electron microscopy (TEM) revealed uniform attachment of CFO nanoparticles to the walls of CNTs, formation of 3D networks in the CFO@CNTs binary composite and its effective encapsulation by PANI. Benefiting from the controllable composition, 3D networking, porous structure of PANI, and strong complementary effect between CFO and CNTs (source of magnetic and dielectric losses), the PANI/CFO@CNTs ternary composite exhibited superior EMI shielding characteristics with a total shielding effectiveness of 16.80 dB corresponding to 97.90 % attenuation at a thickness of 2 mm. Considering the excellent EMI shielding properties, PANI/CFO@CNTs ternary composites can be employed as high-performance EMI shields.

Prospect of Poly(2-chloroaniline)-Nanocomposite-Silica as Anode in Li-Ion Coin Cell

This work evaluates the application of interfacially polymerized poly(2-chloroaniline)-nanocompositesilica (P2ClAni-SiO2), a composite material based on substituted conducting polymer, poly(2-chloroaniline) (P2ClAni) in which silica nanoparticles with varying weight percentages act as fillers. The nanocomposites were characterized by FTIR spectroscopy, XRD, TGA and DSC analysis. The electrochemical characterization of P2ClAni and P2ClAni-SiO2 (10 wt.%) were investigated by cyclic voltammetry, impedance spectroscopy and galvano-static cycling electrochemical measurements. The cyclic voltammogram studies showed broad redox peaks, which correspond to reversibility in transition of leucoemeraldine to emeraldine form of polyaniline. The charge transfer between electrolyte and electrode was represented in the form of Nyquist plot. The galvanostatic cycling test of P2ClAni and P2ClAni-SiO2 showed a discharge capacity of 44.3 mAh g-1 and 69 mAh g-1 for 5 cycles, respectively. P2ClAni-SiO2 composite shows good electrochemical properties and cycling stability compared to P2ClAni. The chlorosubstituted polyaniline with silica demonstrate to be an anode material in lithium ion batteries.

Synthesis and characterization of montmorillonite/polyaniline composites and its usage to modify a commercial separator

Composites of montmorillonite (MMT) and polyaniline (PANI) were synthetized through a facile and inexpensive method. Two samples with different MMT:PANI ratios were studied and deeply characterized by XRD, TG, zeta potential, FTIR and XPS measurements. On one hand, the sample with ratio MMT:PANI = 87:13 was an intercalated composite, were polyaniline resides between the inorganic layers of the clay at a regular distance. On the other hand, the sample with ratio MMT:PANI = 12:88 was an exfoliated composite, where the inorganic sheets are immersed in an amorphous polymeric matrix. FTIR and XRD results indicated that in both samples, the emeraldine form of polyaniline was obtained. The composites were used to modify -by dr. blade technique- a commercial separator for lithium-ion batteries (LIBs) with the aim of increasing its wettability, ionic conductivity and electrochemical performance. The three-dimensional and multilayered network structure of the MMT/PANI composites led to an enhancement of the electrolyte uptake capacity (from 32% in bare separator to 137% and 168% for MMT/PANI_87/13 and MMT/PANI_12/88 modified separators, respectively, after 3 h). The presence of the coating membrane also led to an increase of the ionic conductivity by one order of magnitude in the modified separators respect to the unmodified one. These coated and non-coated separators were used to assemble full cells with LiNi1.5Mn0.5O4 as cathode active material. The capacity fade after 200 cycles was 20% lower in the cell with MMT/PANI_12/88 membrane in comparison with the bare separator. The enhancement of the electrochemical performance of the cells with the coated separator suggests that is a promising strategy to be used in LIBs.

Combined experimental and theoretical investigation of optical and structural properties of poly aniline derivatives

The structure of poly aniline (PANI), poly para phenylenediamine (PpPDA), and poly benzidine (PBz) is strongly dependent on the synthesis conditions and procedure. For this reason there is an ambiguity in the proposed structure of the polymers in the literature. A density functional theory (DFT) calculation were performed to establish the structure of synthesized PANI, PpPDA, and PBz. Different structures were considered for each polymer and fully optimized. Then their electrical and optical properties were calculated. Experimental band gaps of studied polymers were obtained using cyclic voltammetry technique and compared with those calculated by DFT. Optical band gap was also obtained from UV–visible spectrum of each polymer dissolved in DMSO solvent. Optical band gap value obtained for aniline is 1.90 eV which is close to the experimental band gap value reported for emeraldine form of poly aniline. Comparing calculated and experimental HOMO–LUMO gaps decline the formation of benzoid (PPDA-a) and phenenzine (PPDA-b) structures during synthesis of PpPDA. However, the exact structure of PpPDA was recognized through comparing experimental and simulated optical properties. Calculated electronic and optical band gaps of phenanzine structure of synthesized benzidine (PBz-c) are close to those of experimental ones and are confirmed by the spectroscopic results. Obtained results show that theoretical calculations play an important role in the detection of complex polymer structures.

Influence of the polyaniline structure on the properties of epoxy compounds and materials

Rheological properties of epoxy compounds containing pernigraniline and emeraldine forms of polyaniline were studied. The emeraldine form of polyaniline catalyzes the curing of epoxy compounds. The influence of the emeraldine and pernigraniline forms of polyaniline on the glass transition point of epoxy polymeric materials was determined. The elastic and deformation properties of the epoxy polymeric materials were studied. At up to 0.28 wt % content of the emeraldine form of polyaniline, the elastic modulus and ultimate strength increase. Introduction of the pernigraniline form of polyaniline leads to a decrease in the elastic modulus and to an insignificant increase in the ultimate strength of the epoxy polymeric materials.

Preparation and characterization of polyaniline–1‐hydroxyethane 1,1‐diphosphonic acid salt and its application as a catalyst for the synthesis of N‐benzylidine‐2‐phenyl imidazo[1,2‐a]pyridines

ABSTRACTA novel, efficient, and easily synthesizable catalyst, an emeraldine form of polyaniline (PANI)−1‐hydroxyethane 1,1‐diphosphonic acid salt (HEDP), was successfully synthesized and demonstrated as a reusable polymer‐based solid acid catalyst in the synthesis of N‐benzylidine‐2‐phenyl imidazo[1,2‐a]pyridines with 2‐aminopyridine with aromatic aldehydes and trimethyl silylcyanide at room temperature. PANI–HEDP was characterized by Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, and conductivity measurements. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2995–3000, 2013

Chemical modification of polyaniline by N-grafting of polystyrenic chains synthesized via nitroxide-mediated polymerization

This study aims to explore an effective route for the preparation of conductive N-substituted polyaniline (PANI) by the incorporation of brominated poly(styrene-co-p-methylstyrene) onto the emeraldine form of polyaniline. For this purpose, at first, poly(styrene-co-p-methylstyrene) was synthesized via nitroxide-mediated polymerization (NMP), and then, N-bromosuccinimide was used as brominating agent to obtain a copolymer with bromine. Thereafter, deprotonated polyaniline was reacted with brominated poly(styrene-co-p-methylstyrene) to prepare the poly(styrene-co-p-methylstyrene)-graft- polyaniline [(PSt-co-PMSt)-g-PANI] terpolymer through N-grafting reaction. The terpolymer was characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Optical properties of (PSt-co-PMSt)-g-PANI in the undoped and doped states were obtained by ultraviolet-visible spectroscopy (UV-Vis), and electrical conductivity at room temperature was measured using samples in which the conductive materials was sandwiched between two Ni electrodes. Moreover, electroactivity of the synthesized terpolymer was verified under cyclic voltammetric conditions on the surface of the working glassy carbon electrode (GCE). The solubility of (PSt-co-PMSt)-g-PANI terpolymer was examined in common organic solvents, such as, tetrahydrofuran (THF), chloroform and xylene.

Synthesis and characterization of a terpolymer derived from styrene, methyl styrene, and polyaniline and its organoclay nanocomposite

AbstractA synthetic route for the preparation of a novel solution terpolymer derived from styrene, methyl styrene, and polyaniline (PANI) and its organoclay nanocomposite with conductive and mechanical properties is demonstrated. Soluble PANI was synthesized by the incorporation of brominated poly(styrene‐co‐methyl styrene) onto the emeraldine form of PANI. Styrene‐co‐methyl styrene copolymer was synthesized via nitroxide‐mediated living radical polymerization by 2,2,6,6‐tetramethylpiperidinyloxy iniferter and then was brominated with N‐bromosuccinimide. The solution terpolymer derived from styrene, methyl styrene, and PANI was synthesized through the N‐grafting reaction of deprotonated PANI and brominated terpolymer. Nanocomposites of the terpolymer with modified montmorillonite were prepared with a solution intercalation method. The conductivity of the terpolymer was measured by the four‐point probe method. The structures of the intermediate, terpolymer, and nanocomposite were investigated by Fourier transform infrared spectroscopy, 1H‐NMR, and X‐ray diffraction techniques. The molecular weight of the terpolymer was determined by gel permeation chromatography. Their thermal behavior was examined by differential scanning calorimetry and thermogravimetric analyses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Study on soluble polyaniline by positron annihilation technique

The solubility, electrical conductivity, and other properties of polyaniline (PANI) are highly dependent on its oxidation state. In this work, polyaniline (PANI1) prepared by peroxodisulphate induced polymerization of aniline in acidic aqueous medium in presence of benzenediazonium chloride salt was found to exist in lower oxidation state than emeraldine form of PANI and was highly soluble in common organic solvents. This polymer was subjected to positron annihilation spectroscopic study to investigate the correlation between the oxidation state of the polymer and defect sites generated by different degrees of protonation that in turn affect its electrical conductivity. The positron annihilation lifetime data were resolved to yield a three-component fit for PANI1 subjected to different levels of protonation. The variation of positron annihilation parameters (τ1,I2) and Doppler broadening parameters (R, S) as a function of protonation level of the polymer indicate the dopant sites increase initially on protonation and reach a saturation value after a certain level of acidification. The lower value of electrical conductivity and the intensity of intermediate lifetime component (I2) for PANI1 compared to PANI in emeraldine oxidation state indicate the presence of lesser number of quinoid–imine moieties that could undergo protonation and thus yield highly enriched trapping centers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Solid-State Reduction of Silver Nitrate with Polyaniline Base Leading to Conducting Materials

The polyaniline (PANI) base was ball-milled with silver nitrate in the solid state. Samples were prepared at various mole ratios of silver nitrate to PANI constitutional units ranging from 0 to 1.5 for three processing times, 0, 5, and 10 min. The emeraldine form of PANI was oxidized to pernigraniline, and the silver nitrate was reduced to metallic silver. Nitric acid is a byproduct, which may protonate the residual emeraldine and pernigraniline. The changes occurring in the structure of PANI are discussed on the basis of Fourier transform IR and Raman spectroscopies. Raman spectra revealed the formation of pernigraniline salt. The reaction between the two nonconducting components, emeraldine base and silver nitrate, produced a mixture of two conducting components, emeraldine or pernigraniline nitrate and metallic silver. The accompanying conductivity changes were determined. The increase in the conductivity of the original base, 10(-9) S cm(-1), up to 10(-2) S cm(-1) was found to depend on the mole ratio of silver nitrate to PANI base and on the processing time of the components in the ball mill.

The reduction of silver nitrate with various polyaniline salts to polyaniline–silver composites

A conducting polymer, emeraldine form of polyaniline (PANI), reduces silver nitrate to metallic silver. The composites of PANI and silver have been prepared at equimolar proportion of reactants. Seven acids, representing inorganic and organic acids, have been used to protonate PANI. The acids were selected with respect to their chemical indifference or the ability to precipitate or reduce silver(I) ions. The PANI–silver composites differed in the conductivity from 1.7 × 10 −6 S cm −1 when PANI phosphate was used as a substrate to 22.8 S cm −1 for PANI hydrochloride at comparable silver contents, 24 and 27 wt.%. The protonation state of PANI in PANI–silver composites was analyzed by FTIR spectroscopy. The composites contained spherical silver nanoparticles of 40–80 nm in size and also macroscopic particles, irrespective of PANI entering the reaction.

Synthesis and characterization of N‐substituted polyaniline with mesogen molecules

AbstractThe N‐substituted polyaniline (PANi) was synthesized by incorporation of bromine‐terminated mesogens onto the emeraldine form of polyaniline. Firsty three liquid crystalline molecules containing biphenyl units were synthesized. These mesogenic molecules are named as: 6‐bromo‐ (4‐hexyloxy‐biphenyl‐4′‐oxy) hexane (C6C6Br), 5‐bromo‐(4‐hexyloxy‐biphenyl‐4′‐oxy) pentane (C6C5Br), 6‐bromo‐(4‐octyloxy‐biphenyl‐4′‐oxy) hexane (C8C6Br). Differential scanning calorimetry (DSC) in combination with polarizing optical microscopy (POM) were used to investigate the thermal properties of them. Optical microscopy showed focal conic texture characteristic of the Smectic A phase for (C6C5Br) and (C8C6Br). For (C6C6Br) smectic phase was determined. DSC experiments were also found in accord with mesophase formation. For the synthesis of N‐substituted polyaniline with these mesogen molecules, the emeraldine base polyaniline was reacted with BuLi to produce the N‐anionic polyaniline and then deprotonated polyaniline was reacted with bromine‐end mesogen to prepare mesogen‐substituted polyaniline through N‐substitution reaction. The degree of N‐substitution can be controlled by adjusting the molar feed ratio of mesogen to the number of repeat units of PANi. The microstructure and compositions of obtained polymers were characterized by FT‐IR, elemental analysis, DSC, and scanning electron microscopy (SEM). The cyclicvoltammetry show that the electroactivity of N‐substituted polyaniline is strongly dependent on the degree of N‐grafting. The solubility of mesogen‐substituted polyaniline in common organic solvents such as THF and chloroform was improved by increasing the degree of N‐substitution and also the samples are partially soluble in xylene. Liquid crystalline behavior of mesogen‐substituted polyanilines was investigated via POM, but no mesophase was observed. Copyright © 2008 John Wiley & Sons, Ltd.

Effects of polyaniline chain structures on proton conduction in a PEM host matrix

This study examined the effects of the conjugated chain structure of polyaniline (PAn) on proton transport in a proton exchange membrane (PEM) containing a small amount of PAn colloidal particles. The PEM host matrix consisted of a hydrophobic three-component polymer blend (TCPB) of poly(4-vinylphenol- co-methylmethacrylate) P(4-VP-MMA), poly(butyl methacrylate) (PBMA), and Paraloid ® B-82 acrylic copolymer resins; in which a hydrophilic network of 2-acrylamido-2-methyl propanesulfonic acid (AMPS), 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol)dimethylacrylate (PEGDMA) was formed upon embedded polymerization. Colloidal PAn particles were added to the PEM matrix during the embedded polymerization of PEM. Two types of PAn colloidal particles with different chain structures and morphologies were synthesized by inverse miniemulsion polymerization and interfacial polymerization. The PAn(1) particles from inverse miniemulsion polymerization were bar-shaped, contained a higher fraction of quinoid diimine units than the scaffold-like PAn(2) particles from interfacial polymerization, and displayed a strong promotional effect on proton conduction. The oxidation state of the PAn particles was also varied by post-synthesis treatments to evaluate the effect of oxidation state on proton conduction. It was found that a mixed oxidation state such as the emeraldine form of PAn had the best enhancement effect. The PAn loading optimal for proton conductivity enhancement of the composite PEM was determined to be about 2 wt% of PAn(1).

Chemical modification of polyaniline by N-grafting of polystyrene synthesized via ATRP

The N-substituted polyaniline (PANi) was synthesized by incorporation of bromine-terminated polystyrene (PS-Br) onto the emeraldine form of polyaniline. End brominated polystyrene was synthesized by atom transfer radical polymerization (ATRP) technique and then deprotonated polyaniline was reacted with PS-Br to prepare PS-grafted PANi (PS-g-PANi) copolymer through N-grafting reaction. The degree of N-grafting can be controlled by adjusting the molar feed ratio of PS-Br to the number of repeat units of PANi. The microstructure and compositions of the PS-g-PANi copolymers with different degrees of N-substitution were characterized by FT-IR, elemental analysis, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The cyclicvoltammetry shows that the electroactivity of N-substituted PANi is strongly dependent on the degree of N-grafting. The solubility of PS-g-PANi copolymers in common organic solvents such as tetrahydrofuran and chloroform was improved by increasing the degree of N-grafting, and also the samples are partially soluble in xylene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Polymerization of aniline on copper phosphonate materials

We report the use of layered copper phosphonate materials for the oxidative polymerization of aniline. The use of copper carboxyethylphosphonate results in the formation of the perinigraniline form of polyaniline in the interlayer region of the host structure, giving rise to an increase in the interlayer spacing by 10.2 Å. For copper phenylphosphonate, the emeraldine form of polyaniline is generated, although there is no evidence for intercalation within the interlayer region of the host material. Copper methylphosphonate is destroyed during the process of polymerization of aniline, yielding bulk copper metal as the only solid product. The results demonstrate the diversity of behaviour that may result from the use of structurally related, although chemically different, host materials for the polymerization of aniline.

Impedance Study of the Charge‐Transfer Interaction Between the Polyaniline Chain and Redox Pair in Solution

The impedance method was used to study the charge‐transfer interaction between the polymer conducting chain (emeraldine form of polyaniline, PANI) and active molecules in solution (tetrafluorohydroquinone, 4F‐Hqui). Equivalent electrical circuits were found for steady‐state potentials of the PANI electrode and their parameters were analyzed as dependent on pH. In the presence of 4F‐Hqui in the pH range −0.3 to 3, active molecules appear in the double electrical layer and alter the charge exchange between electrode and solution (extrinsic reaction) and faradaic charging of PANI (intrinsic process). Charge‐transfer (CT) resistance increases with respect to acid‐only solutions; nevertheless, conductivity through the polymer still limits electrical transport at low frequencies. In low pH solutions the protonated imine centers of PANI interact with hydroquinone molecules forming H bonds along the polymer chain. We have proposed that such a structure could serve as an electron path in the moment of the charge transfer. When pH is increased above seven, the CT complex decomposes irreversibly, the polymer electrode is modified and loses its conductivity. We have proposed and discussed possible chemical structures for the modified polymer, its acid transformation, and electrochemical doping. © 2000 The Electrochemical Society. All rights reserved.

In situ FTIR–attenuated total reflection spectroscopic investigations on the base–acid transitions of polyaniline. Base–acid transition in the emeraldine form of polyaniline

Emeraldine refers to the semi-oxidized state of polyaniline and it can exist in the base form or the protonated form (salt) generated by treatment of the base form with an acid. Using a newly applied doping system NaReO4/HReO4, the investigation of the base–acid transition process of emeraldine has been carried out by ex situ and in situ FTIR spectroscopic methods. In situ FTIR–ATR (attenuated total reflection) measurements performed during the base–acid transition process clearly show the change in the structure of the polymer film observable. The physical properties of emeraldine can be changed considerably by varying the pH of the media. The base form of emeraldine is an insulator and treatment with acidic media results in the highly conducting salt form (proton doping). The protonation of emeraldine starts at pH 6. The intensity of a broad absorption band at wavenumbers higher than 2000 cm–1(0.25 eV) depends strongly on the pH of the electrolyte. This absorption band bleaches completely with increasing pH, indicating a strong correlation between this band and the metallic character of the polymer. On the basis of in situ FTIR–ATR measurements, a reaction path of acid–base transitions has been proposed.

Measurement of the charge in a double layer at a solid/liquid interface: use of a conducting polymer

A method is described for measuring the equilibrium double layer charge at the interface between an aqueous solution of HCl and NaCl and the emeraldine form of polyaniline. The method involves the analysis of the measured change in double layer potential that attends the transfer of a polyaniline electrode from a reference solution to one having a different pH. Both experiment and theory are presented

New Transport Mechanisms for Conducting Polymers: The Role of Disorder

Abstract A unified view of the metallic state in polyaniline and heavily-doped polacetylene is presented. We first consider a single randomly-protonated strand of the emeraldine form of polyaniline. We show explicitly that the disorder inherent in this system is described by the random-dimer model of Dunlap, Wu and Phillips1. The random dimer model is simply a tight-binding model for a binary alloy in which pairs of lattice sites are assigned one of two values at random. The random dimer model is shown to possess a narrow band of conducting states that can ultimately lead to dramatic increases in the conductivity if the Fermi level is appropriately tuned. It is demonstrated explicitly that the location in the energy band of the conducting states of the random-dimer model for polyaniline coincides with recent calculations of the location of the Fermi level in the protonated form of the polymer2,3. We argue then that the random-dimer model is capable of explaining the insulator-metal transition in polyanili...

The study of conducting polymer interaction with gaseous substances IV. The water content influence on polyaniline crystal structure and conductivity

At present the water influence on the polymer crystal structure is poorly studied. Water molecules may interact with the polymer chain active sites during synthesis as well as in the processes of water adsorption from moist air. The thermoprogrammed desorption, conductivity measurement, X-ray phase analysis and high-resolution ESR techniques have been employed to study the interaction of water vapour with an emeraldine form of polyaniline (PANI). It is concluded that water influences the crystal structure of PANI and in this way changes its conductivity.