Polyaniline HCl Research Articles

Investigation of optical and electrical properties of piperic acid-filled polyaniline composites

In this study, the electrical and optical properties of the piperic acid (PA)-filled polyaniline-HCl (PANI-HCl) composites (PANI-HCl/PA) were investigated. For this purpose, the composites containing different weight ratios of PA were prepared by the oxidative chemical polymerization of PANI-HCl. The studies on the optical properties of the pristine PANI-HCl and the composites showed that the bandgap of the PANI-HCl reduced from 2.510 to 2.490 eV with the addition of 3% PA. Additionally, significant alterations such as redshift, improved polarizability, and tuned refractive were observed. From the thermoelectric analyses, it was obtained that the electrical conductivity of the pristine PANI-HCl increased from 0.042 up to 37.5 Scm−1 while the Seebeck coefficient increased from 10.1 up to 49.1 µVK−1. The thermoelectric power factor of the composites reached the maximum at 3.91 µWm−1K−2, which is approximately 104 times higher compared to the pristine PANI-HCl. Given the significant changes such as redshift, band gap narrowing, improved polarizability, tuned refractive index, and enhanced thermoelectric performance, this study suggests that the composites prepared in this study could be used as efficient materials for the design and development of UV shielding and thermoelectric materials.

Some Specific Features in the Applying the Method of Raman Spectroelectrochemistry while Studying Polyaniline Electrosynthesis in Polymeric-Acid Medium

Initial stages of aniline galvanostatic polymerization at platinum electrode in aqueous solutions of poly-2-acrylamido-2-methyl-1-propansulfonic acid and polystyrenesulfonic acid are studied by the method of Raman spectroelectrochemistry. A laser with wavelength of 532 nm excited the Raman scattering. The very presence of intermolecular associates able to luminescence in the polyacid solution (in the case of polystyrenesulfonic acid) was shown to result in the Raman-spectrometer photodetector overload if normal incidence of laser beam at the electrode (the angle 0°) was used. The Raman-spectrometer photodetector overload can be avoided by the varying of the incidence angle over the 0°–20° range, even without using other techniques (leading to a decrease in the reliability of the studied Raman band registration, such as the lowering of the integration time, intensity or energy of the excitation). Comparative study of aniline electropolymerization in the presence of poly-2-acrylamido-2-methyl-1-propansulfonic acid, polystyrenesulfonic acid, and HCl revealed some characteristic bands in the Raman spectra of the polyaniline–polyacid complexes in the Raman frequency range from 2000 to 3000 сm–1; these bands relate to the polyacid’s backbone and are absent in the Raman spectra of the polyaniline–HCl film. The dynamics of changes in the contribution to the integral Raman spectrum of the band of radical-cations (1330–1350 сm–1) characterizing the highly conductive emeraldine form of polyaniline was compared for the polymerization media. In the course of the electrosynthesis it was found, that the accumulation rate of these species in the film decreased in the series poly-2-acrylamido-2-methyl-1-propansulfonic acid > HCl > polystyrenesulfonic acid.

Raman spectroelectrochemical study of electrodeposited polyaniline doped with polymeric sulfonic acids of different structures

Polyaniline (PANI) films were prepared by electrochemical polymerization of aniline on Pt-electrode in aqueous medium in the presence of polymeric sulfonic acids distinguished by different flexibility of the polymer chain: (1) poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA, flexible chain); (2) poly(4-styrenesulfonic acid) (PSSA, flexible chain), (3) poly-4,4′-(2,2′-disulfoacid)-diphenylene-iso-phthalamide (i-PASA, semi-rigid chain); and (4) poly-4,4′-(2,2′-disulfoacid)-diphelylene-tere-phthalamide (t-PASA, rigid chain). Raman spectroelectrochemical studies using 532 nm laser excitation were carried out in aqueous HCl. The conventional HCl-doped PANI films were also studied for comparison. The results allowed one to distinguish the potential-dependent vibrations belonging to PANI and potential-independent vibrations belonging to the polyacids. In addition, amide C=O vibration was separated in the spectra by comparing the results for amide-containing (PAMPSA, i-PASA, and t-PASA) and amide-free (PSSA) PANI-polyacid complexes. The films of PANI-polyacid complexes demonstrated increased content of radical cation moieties at low potentials compared to PANI–HCl films.

Polyaniline/poly(ethylene terephthalate) film as a new optical sensing material

Thin polyaniline (PANI) films are known as good optical gas sensors to ammonia but have weak mechanical properties that limit their industrial applications. To improve these properties we have developed new robust transparent PANI based composite films using the combination of aniline polymerization inside a thin (∼1μm) surface layer of a poly(ethylene terephthalate) (PET) film and specific chemical treatments. We demonstrate that the final PANI/PET composite films have an increased surface area; give strong, fast and reversible optical sensor responses to ammonia or formic acid gas mixtures when in doped or dedoped PANI states respectively. Specifically in case of ammonia–air gas mixtures we demonstrate that the doped (PANI–HCl)/PET films give linear optical responses to ammonia gas in concentration ranges of 5–200ppm and 200–920ppm. The undoped PANI/PET films give linear optical response to formic acid in the concentration ranges of 15–200ppm and 200–1600ppm.

Synthesis of Processable Polyaniline and its Anticorrosion Performance on 316LN Stainless Steel

The soluble polyaniline (PANI) salts were synthesized by chemical-oxidative polymerization of aniline using sodium dodecylbenzene sulfonic acid, camphor sulphonic acid and hydrochloric acid as dopants and ammonium per sulphate (APS) as an oxidant. The synthesized PANI were characterized by X-ray diffraction, scanning electron microscope, Fourier transform-infrared spectroscopy and thermogravimetric analysis. It is found that the yield of PANI, electrical conductivity, solubility and thermal stability varies with the dopants and the stoichiometrics of monomer/dopant ratios. The PANI doped sample follows the solubility order as: PANI–SDBS > PANI–CSA > PANI–HCl. Thermal stability of PANI–CSA is grater than PANI–SDBS and PANI–HCl. XRD pattern shows the higher crystallinity for HCl and CSA doped PANI while SDBS doped PANI shows the poor crystallinity. SEM study revealed the partially crystalline and agglomerated morphology of the polymer. According to the results, the corrosion rate or corrosion current of PANI–SDBS salts coated samples varies with molar ratios of SDBS to aniline and the optimum molar ratio of PANI–SDBS coating to achieve the best anticorrosive performance on 316LN SS is 2.5 mol mol−1.

Exceptional ion-exchange selectivity for perchlorate based on polyaniline films

Polyaniline (PANI) films were electrochemically synthesized on graphite electrode and their ion-exchange selectivities for ClO 4 − were investigated. Cyclic voltammetry (CV) results showed that PANI-H 2SO 4 film represented higher selectivity for ClO 4 − than PANI–HCl and PANI–HClO 4. Furthermore, the CV records of PANI–H 2SO 4 film in different acidic solutions demonstrated that ClO 4 − exchange was performed in a lower potential range (from −0.025 V to 0.097 V), which is distinguished from SO 4 2− and Cl −. Additionally, chronoamperomertry (CA) studies of PANI–H 2SO 4 film in 0.1 M various acidic solutions (H 2SO 4, HCl and HClO 4) confirmed that the diffusion coefficient values in HClO 4 (13.319/18.184 × 10 −6 cm 2 s −1) were the biggest during doping/de-doping process. The exceptional ion-exchange selectivity for ClO 4 − was explained by the process of dominant accumulation, quick insertion of anions, and the sluggish mobility of ClO 4 − inside the membrane. Results of present work demonstrated that PANI may serve as a promising membrane for ClO 4 − removal by ion-exchange process.

Electrically conductive nanocomposites of polyaniline with poly(vinyl alcohol) and methylcellulose

AbstractElectrically conductive nanocomposites of HCl‐doped polyaniline (PANI–HCl) nanocolloid particles with water‐soluble and film‐forming polymers such as poly(vinyl alcohol) (PVA) and methylcellulose (MC) were prepared by the redispersion of preformed MC‐coated submicrometric PANI–HCl particles in PVA and MC solutions under sonication for 1 h and the casting of the films from the dispersions followed by drying. The submicrometric polyaniline (PANI) particles were prepared by the oxidative dispersion polymerization of aniline in an acidic (1.25M HCl) aqueous ethanol (30 : 70) medium with MC as a steric stabilizer. The particles contained 4.7 wt % MC and had a conductivity of 7.4 S/cm. They had an oblong shape of 203 nm (length) and 137 nm (breadth). Sonication broke the oblong‐shaped particles to sizes of ∼10 nm in the PVA matrix and ∼60 nm in the MC matrix. The electrical conductivity of these films was measured, and the percolation threshold was determined. The composites had the characteristics of a low percolation threshold at a volume fraction of PANI of 2.5 × 10−2 in the PVA matrix and at a volume fraction of 3.7 × 10−2 in the MC matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Redox reactions of polyaniline films doped with d, l-camphor sulfonic acid

Simplified comparison of standard redox potentials demonstrates that redox reactions of d, l-camphor sulfonic acid (CSA) doped polyaniline (PANI) films with aqueous solutions of FeCl 3 and K 3Fe(CN) 6 should not take place. Nevertheless the reactions are possible and described here. The initial rate of 0.01M Fe 3+ reduction is higher than that obtained with HCl doped PANI film at similar conditions. Films doped with CSA stay active at neutral pH with K 3Fe(CN) 6 as the oxidizing agent, which is different from depressed electroactivity of PANI–HCl films in these conditions. The redox processes are not limited by simple surface reaction and have two kinetically different steps (the initial, fast and the second, slower). A new mechanism is suggested according to which two redox half reactions (oxidation of the polymer fragments and reduction of ions in the solution) are separated in space and are coupled by counter transport of electrons and Cl − anions into the opposite direction. A new phenomenon is demonstrated where the gradient of Cl − activity in the film changes the equilibrium state of the redox process in aqueous solution.

Effect of magnetic field on properties of polyaniline doped with dysprosium chloride

The polyaniline doped with DyCl 3 under different magnetism of magnetic field (polyaniline/DyCl 3/Bp) have been prepared in solution containing 0.5 mol dm −3 DyCl 3. Their conductivity, UV–vis and FT-IR spectra and X-ray diffraction (XRD) were investigated. The experimental results from UV–vis and FT-IR spectra showed that there exists the orientation effect of the polymer in magnetic field and the cooperative effect of Dy 3+ and magnetic field. Due to these effects, the conductivity of the polymer is dependent on magnetism, and polyaniline/DyCl 3/Bp exhibit the higher degree of crystallinity than that of polyaniline–HCl.

Effect of sulphuric acid on the properties of polyaniline–HCl salt and its base

The effect of H 2SO 4 on polyaniline–HCl salt and its base was studied for different concentrations of the acid (0.1, 1.0, 4.0, 8.0, 13.0 and 18.0 M) for a duration of one day and five days. The H 2SO 4 treated polyaniline samples were characterised by conductivity and UV–vis, FT-IR and EPR spectroscopic measurements. Due to the incorporation of H 2SO 4 in the polymer chain significant effects on polyaniline–HCl salt were observed, while for the polyaniline base doping occurs depending on the concentration of H 2SO 4. The extent of doping and the incorporation of the sulphate group in the polymer chain are revealed by the spectroscopic and conductivity studies. The conversion of polyaniline base to the salt form is less efficient by H 2SO 4 doping when compared to doping by HCl.

Influence of high-energy electron irradiation on the conduction behavior of doped polyaniline films in the high current density regime

The influence of high-energy electron irradiation on the conduction behavior at high current density of polyaniline (PANI) films doped with HCl and camphor sulfonic acid (HCSA), respectively, is reported. It is found that there exists an ohmic region under certain current density for both non-irradiated and irradiated samples. No significant change of the conductivity and maximum current density are observed if the sample is irradiated at room temperature and low dosage. The conductivity and maximum current density decrease with dosage if the samples are irradiated at high temperature. However, after redoping with 1 M HCl, the conductivity of these films can be recovered, while the maximum current density remains at a lower level. The DSC thermograms show that the crosslinking density of PANI–HCl film increases due to the high-energy electron irradiation.

In situ doping polymerization of polyaniline microtubules in the presence of ?-naphthalenesulfonic acid

Conducting microtubules of Polyaniline (PANI) were synthesized for the first time by the “in situ doping polymerization” method in the presence of β-naphthal- enesulfonic acid (NSA) as dopant. Different doping methods, such as “immerse doping” and “grind doping,” and different synthetic conditions, such as molar ratio of aniline (An) to NSA (An/NSA), concentration of NSA in the polymerization media, reaction temperature, and time were investigated to understand the formation of microtubules. It was found that the PANI–NSA microtubules can be formed only by the “in situ doping polymerization” method, and the above synthetic conditions strongly affect the formation of the PANI–NSA microtubules, especially the molar ratio of An to NSA. An optimal condition was found under which tubules with 1–3 μm in diameter and 10–50 μm in length were obtained. The morphology of PANI–NSA tubules was proved by SEM and TEM, and their backbone structure was characterized by FTIR, UV-VIS, XPS, and X-ray diffraction. Results of these measurements showed that the molecular structures of the resulted PANI–NSA microtubules were identical to that of PANI–HCl synthesized by conventional method. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 151–157, 1999

Stability of polyaniline synthesized by a doping-dedoping-redoping method

Stability, including thermal stability, conductivity stability in air and after thermal treatment (100–200°C), of the polyaniline (PANI) films synthesized by a doping–dedoping–redoping method was investigated. It was found that thermogravimetric analysis (TGA) curves undergo three steps: loss of water or solvent, dedoping and decomposition, and those depend on the counterions. Compared with PANI films doped with camphor sulfonic acid (CSA) in m-cresol, the thermal stability of the doped PANI films is improved by the new method, and thermal stability in the order of PANI–H3PO4 > PANI–p-TSA > PANI–H2SO4 > PANI–HCl, PANI–HClO4 > PANI–CSA was observed. The conductivity of the doped PANI films at room temperature was reduced after thermal treatment, and it is dependent of the counterions. It was found that the conductivity stability of PANI–p-TSA and PANI–CSA is the best below 200°C. When the doped PANI films were placed in air, their conductivity decrease slowly with time due to deproton, and also depends on the counterions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 615–621, 1999

Annealing effect on the electrochemical property of polyaniline complexed with various acids

The annealing effect on the electroactivity of polyaniline (PAn) complexed with various acids has been investigated. The polyaniline— p-toluene sulfonic acid complex (PAn— pTSA) and polyaniline—hydrochloric acid complex (PAn—HCl) show decreased electroactivities with annealing temperature, but the polyaniline—dodecylbenzene sulfonic acid complex (PAn—DBSA) shows an increase in electroactivity up to an annealing process of 150°C, and then a decrease at an annealing process of 180°C. The increase of the electroactivity for PAn—DBSA can be explained by an additional thermal doping of undoped DBSA with annealing. The electrical conductivities at a high temperature of 230°C are in the order of PAn— pTSA > PAn—DBSA > PAn—HCl. PAn— pTSA shows the highest conductivity because pTSA shows the most thermal stability. Decreased conductivity at a high temperature may be due to the dedoping and structural change that cannot be recovered by redoping.

ZnCl 2-induced changes in the electronic properties of polyaniline—HCl salt and its base

The effects of ZnCl 2 on the electronic properties of polyaniline—HCl salt and its base were studied for different concentrations of ZnCl 2 (0.1, 1.0, 3.0 and 6.0 M) for 1 and 5 days. The polyaniline samples were characterized by conductivity and spectroscopic measurements such as UV-Vis, FT-IR and EPR. ZnCl 2 treatment results in the degradation of the polyaniline salt and, for the polyaniline base, doping occurs depending on the concentration of ZnCl 2. The conversion of polyaniline base to polyaniline salt is less efficient in the case of ZnCl 2 doping when compared to doping with HCl. There is no significant change in the properties of polyaniline salt and base with increase in duration of ZnCl 2 treatment. The poor charge storage capacity and shelf-life of the polyaniline—zinc cell system can be understood from the present study.