Polyaniline Samples Research Articles

Membrane electrode assembly with doped polyaniline interlayer for proton exchange membrane fuel cells under low relative humidity conditions

A membrane electrode assembly (MEA) was designed by incorporating an interlayer between the catalyst layer and the gas diffusion layer (GDL) to improve the low relative humidity (RH) performance of proton exchange membrane fuel cells (PEMFCs). On the top of the micro-porous layer of the GDL, a thin layer of doped polyaniline (PANI) was deposited to retain moisture content in order to maintain the electrolyte moist, especially when the fuel cell is working at lower RH conditions, which is typical for automotive applications. The surface morphology and wetting angle characteristics of the GDLs coated with doped PANI samples were examined using FESEM and Goniometer, respectively. The surface modified GDLs fabricated into MEAs were evaluated in single cell PEMFC between 50 and 100% RH conditions using H2 and O2 as reactants at ambient pressure. It was observed that the MEA with camphor sulfonic acid doped PANI interlayer showed an excellent fuel cell performance at all RH conditions including that at 50% at 80 °C using H2 and O2.

Photoluminescence, FTIR, and electrical characterization of samarium(III) chloride‐doped polyaniline

AbstractThe synthesized polyaniline (PANI) is doped with different concentrations of Samarium(III) chloride (SmCl3). The electrical conductivity of doped PANI samples has been measured in the temperature range (300–400K). It has been found that dc conductivity increases with the increase of dopant concentration. Different parameters, based on the conductivity, such as pre‐exponential factor (σ0) and activation energy (ΔE) have also been calculated. These parameters exhibit information about the nature and suitability of the dopant. Doped samples are characterized by FTIR and photoluminescence studies, which show the interaction of dopant with PANI. Two sharp peaks of different intensities from PL spectra at 388 and 604nm have appeared in doped PANI, which might be due to the effect of SmCl3. It has been observed that SmCl3 (dopant) shows noticeable changes in the electrical and spectroscopic properties of doped PANI. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Simplifying the reaction system for the preparation of polyaniline nanofibers: Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media

In this study, several polyaniline samples were prepared by oxidative chemical polymerization using only aniline, (NH 4) 2S 2O 8 and HCl in aqueous media at room temperature for morphological studies by SEM (scanning electron microscopy). The results show that polyaniline nanofibers can be obtained by template-free oxidative chemical polymerization in a conventional low-pH acidic aqueous medium (pH ∼ 0) at room temperature. The study indicates that it is crucial to employ a mild post-polymerization processing procedure, such as dialysis, to preserve the as-formed morphology of polyaniline nanofibers. Our study also suggests that polyaniline could adopt the nanofiber structure as its intrinsic morphology when it is synthesized in a simple oxidative chemical polymerization system consisting of only aniline, (NH 4) 2S 2O 8 and HCl in an aqueous medium at room temperature.

Positron beam studies on polyaniline and Ag-coated polyaniline

The effect of doping of the polyaniline emeraldine base (PEB), with Ni as well as Ni over layer coating has been investigated using variable low energy positron beam. Depth-resolved Doppler S-parameter measurements have been performed on undoped, Ni-doped polyaniline (PANI), and Ag (40 nm) film deposited PANI samples. Significant variation in S-parameter is observed for undoped and Ni-doped PANI. The size of the free volume hole has shifted to lower values upon doping with Ni as compared to that of undoped PANI, which is consistent with the conductivity measurements. For Ag-coated PANI systems, the S vs. E p curves show distinct changes at the surface and interior regions. These results are discussed in the light of changes in free volume hole size distribution.

Studies on the high electronic energy deposition in polyaniline thin films

We report here the physico-chemical changes brought about by high electronic energy deposition of gold ions in HCl doped polyaniline (PANI) thin films. PANI thin films were synthesized by in situ polymerization technique. The as-synthesized PANI thin films of thickness 160nm were irradiated using Au7+ ion of 100MeV energy at different fluences, namely, 5×1011ions/cm2 and 5×1012ions/cm2, respectively. A significant change was seen after irradiation in electrical and photo conductivity, which may be related to increased carrier concentration, and structural modifications in the polymer film. In addition, the high electronic energy deposition showed other effects like cross-linking of polymer chains, bond breaking and creation of defect sites. AFM observations revealed mountainous type features in all (before and after irradiation) PANI samples. The average size (diameter) and density of such mountainous clusters were found to be related with the ion fluence. The AFM profiles also showed change in the surface roughness of the films with respect to irradiation, which is one of the peculiarity of the high electronic energy deposition technique.

Electrical and spectroscopic characterization of polyaniline–polyvinyl chloride (PANI–PVC) blends doped with sodium thiosulphate

Polyaniline is doped with sodium thiosulphate in aqueous tetrahydrofuran (THF) and the blended films have been prepared by changing the amount of doped polyaniline (PANI) in the fixed amount of polyvinyl chloride (PVC). The electrical conductivity of various samples of polyaniline–polyvinyl chloride (PANI–PVC) blends has been studied to see the effect of dopant in the temperature range 300–400 K. Mott's parameters are used to explain the conduction mechanism. Different parameters such as pre-exponential factor ( σ 0), activation energy (Δ E) and T 0 have also been calculated to see the effect of chemical doping. The crystallinity of the blends is explained on the basis of T 0. The calculated values of T 0 show that crystallinity increases with an increase of doped PANI in PANI–PVC blends. Fourier transform-infrared (FTIR) spectroscopy is done to explore the nature and interaction of dopant into the polymeric chain.

Formation of Polyaniline Nanofibers: A Morphological Study

Polyaniline (PANI) powders were prepared by solution precipitation, rapid mixing polymerization, and interfacial polymerization to find the key factors that influence the formation and growth of PANI nanofibers. In chemical oxidative polymerization of aniline, the morphology of the product is mainly determined by aniline concentration. In the case of lower aniline concentration, PANI nanofibers were formed and can be preserved and collected as final product, while in the case of higher aniline concentration, larger sized PANI particles or agglomerates were obtained owing to the growth of the nanofibers. Without participation of the oxidizing step, solid PANI samples with compact structures and dissimilar morphologies were achieved by random accumulation of PANI molecules.

Polyaniline and polypyrrole coatings on aluminum for PEM fuel cell bipolar plates

The conducting polymers polypyrrole and polyaniline were deposited on 6061 aluminum using cyclic voltammetry and painting, respectively. These samples are intended for proton exchange membrane fuel cell applications where surface contact resistance as well as bulk corrosion resistance are requirements for the bipolar plates that separate the cells. Corrosion current and voltage were measured on the samples as well as contact resistance between coated samples as a function of contact pressure. The polypyrrole samples showed neither improved corrosion resistance nor acceptable contact resistance. The painted polyaniline samples, however, showed about an order of magnitude reduction in corrosion current with only a minor increase in contact resistance. It is believed that in the more acidic environment of a fuel cell, the polyaniline will become even more conductive and that further reduction in contact resistance should be possible.

Electrical and humidity sensing properties of synthesized hydrophosphoric acid doped polyaniline

AbstractH3PO4 doped polyaniline was synthesized by a single‐step chemical polymerization method using ammonium persulfate as an oxidizing agent. The material characterization was done by SEM, UV–vis spectroscopy and thermogravimetric analysis (TGA). The pellets of the synthesized material were used to study the electrical properties, using a four‐probe method. The room temperature electrical conductivity is found to be 0.2201 S/cm. The electrical resistance in response to the varying humid environment (ranging between 20 and 100% RH) is recorded to evaluate the sensitivity of the H3PO4 polyaniline samples toward humidity. The resistance of the samples is found to vary by three orders of magnitude for 20–100% RH and is found to decrease with increasing humidity. The response and recovery time are observed to be 12–14 and 26–30 sec, respectively. Copyright © 2007 John Wiley & Sons, Ltd.

Evaluation of the inelastic mean free path (IMFP) of electrons in polyaniline and polyacetylene samples obtained from elastic peak electron spectroscopy (EPES)

Abstract The inelastic mean free path (IMFP) of electrons was determined experimentally for selected polyaniline and polyacetylene samples with Ag and Ni references using elastic peak electron spectroscopy (EPES). The surface composition was determined by XPS and density by helium pycnometry. The high resolution hemispherical ESA-31 and ADES-400 spectrometers were used for measurements in the energy range E = 0.5–3.0 keV and E =0.4 − 1.6 keV, respectively. The integrated elastic peak intensity ratios for sample and reference were calculated using the Monte Carlo (MC) algorithm based on the electron elastic scattering cross-sections database NIST SRD64 version 3.1 and applying TPP-2M IMFPs for polymers. Surface excitation parameters (SEP) and material parameters (ach) for polymers were determined, using the model of Chen, from comparison of measured and MC calculated elastic peak intensity ratios. These corrections proved to be efficient in decreasing the percentage deviations between the obtained IMFPs and the TPP-2M formula IMFPs. The elastic peak of hydrogen was observed in the EPES spectra of polymers. The experimental contribution of the hydrogen to the total elastic peak was 0.58%, while this value obtained from the MC simulations was 1.98%.

Humidity sensing; using polyaniline/Mn3O4 composite doped with organic/inorganic acids

The polyaniline/Mn3O4 composite doped with perchloric acid, sulphuric acid, ortho-phosphoric acid, acetic acid and acrylic acid have been characterized as sensing materials to determine relative humidity in the range of 20–90%. Each composite sample has been used in the form of pellet. Relative humidity measurement has been related with the change in resistance of doped composite samples. Each acid doped polyaniline/Mn3O4 showed an increase in resistance as relative humidity increases, however the sensitivity is found to dependent on the type of dopant anions. The response of each composite is found to be almost linear with the humidity but the composites doped with organic acids have found to be more sensitive than those with inorganic dopants. However polyaniline samples doped with these acids under similar conditions showed reverse behaviour that is the resistance decreases with the increase in relative humidity but with lower sensitivity. The anomalous behaviour of the acid doped composite samples may be due to lowering of p-type nature of the polymer chains in the composites with an increase of humidity. Due to the linear increase in resistance of composites doped with organic acids can act as humidity sensor.

Mesoporous polyaniline having high conductivity at room temperature

We report a new method to synthesize nanostructured polyaniline by using the self-assembly of a mixture of an anionic surfactant sodium dodecylsulfate (SDS) and a non-ionic surfactant, Brij 35 (C 12H 25-(OC 2H 4) 23-OH, a polyether and aliphatic hydrocarbon chain surfactant) as structure directing agents (SDA). The in situ polymerization of aniline was carried out at 277–278 K in the presence of these SDAs with ammonium persulfate as the oxidant. Mesophase formation of the product polymer composites was studied with or without the addition of a co-surfactant molecule or by changing other synthesis parameters. Powder X-ray diffraction and transmission electron microscopic studies suggested wormhole-like disordered structure. N 2 adsorption studies suggested the existence of mesopores with pore widths varying from small to large mesopores in these nanostructured materials, after the removal of the SDAs. The chemical bonding and electronic structure of the mesoporous polyaniline samples were also studied by FT-IR and UV–visible spectroscopic studies. These mesoporous polyaniline samples showed excellent luminescence and conducting properties at room temperature. These π-conjugated polymeric nanomaterials have huge potential in the fabrication of sensors, microelectronic, photo-devices and organic LEDs.

Eco-friendly synthesis of high-quality polyaniline using a copper(ii) scorpionate catalyst

High-quality polyaniline with conductivity reaching 5 S cm−1 has been prepared catalytically in acetonitrile using aniline, HCl, hydrogen peroxide, and 2 mol% of the copper catalyst methyl[tris(3-mesityl-1-pyrazolyl)borato]copper(II) chloride ([MeB(3-(Mes)Pz)3]CuCl). The use of CuCl2·2H2O catalyst instead of [MeB(3-(Mes)Pz)3]CuCl and the solvent effects were also investigated. Polyaniline samples were characterized using CHN analysis, UV-visible spectroscopy, FT-IR spectroscopy, bulk conductivity measurements, cyclic voltammetry and electrochemical impedance spectroscopy. Results of these mutually independent techniques are consistent and indicate the formation of good quality emeraldine form of polyaniline from the [MeB(3-(Mes)Pz)3]CuCl catalyzed reaction in acetonitrile. The conductivity of the polymer prepared using [MeB(3-(Mes)Pz)3]CuCl catalyst depends strongly on the medium of preparation which follows the order acetonitrile > 1 : 1 acetonitrile–water mixture > water. The polymer prepared using CuCl2·2H2O instead of [MeB(3-(Mes)Pz)3]CuCl in a 1 : 1 acetonitrile–water mixture is of relatively poor quality and has a lower conductivity. HCl is also important for the formation of better quality polyaniline and higher yield.

Effects of gamma irradiation on PMMA/polyaniline nanofibre composites

Polyaniline (PANI) presents promising antioxidant and radical-scavenging properties. Substances having these characteristics are good candidates for radioprotecting agents. In this work, nanofibres of polyaniline emeraldine doped with (?)-camphor-10-sulfonic acid (PANI-(?)-CSA) were prepared by self-assembly method under 'silent' and sonochemical conditions. PANI emeraldine base (PANI-EB) nanofibres were obtained after dedoping with NH4OH and were used as additives in films of commercial PMMA, in order to investigate radiostabilising effects on the PMMA matrix. Films containing aniline (An) and PANI-EB grains were also prepared for comparison. Variations in viscosity-average molar mass (Mv) at a 25 kGy dose showed that samples containing aniline, PANI-EB nanofibres or grains in amounts of 0.15% (wt/wt) underwent less degradation than the control sample. In addition, PMMA/PANI-EB nanofibres and PMMA/An at 0.15% (wt/wt) showed a smaller number of scissions per original molecule (α) than control samples in the 25?75 kGy dose range. Spectroscopic characterisation (FTIR, UV-Vis) and scanning electron microscopy (SEM) of PANI samples were also performed.

Optical studies of polyaniline nanostructures

An investigative infrared spectroscopic study is undertaken of nano polyaniline (PANI) samples differing in size and morphology in order to explore the sensitivity of spectral behavior on these factors. IR spectroscopy is used for studying the changes in the interaction between polymeric molecules as parts of nanodimensional structures. A time dependent interfacial oxidative polymerization of aniline monomer is conducted in order to obtain the desired nano PANI samples in doped form. The morphological changes in samples so obtained are characterized using scanning electron microscopy (SEM). The SEM images of samples obtained using the time dependent interfacial polymerization show preferential formation of 1D nano/micro structures with dimensions varying with reaction time intervals, which is also confirmed by transmission electron microscopy (TEM). X-ray diffraction study is undertaken to assess the crystalline nature of the samples. The IR spectra and the X-ray diffraction pattern of samples reflect these morphological variations. A comparative study of bulk polyaniline sample obtained using standard procedures is also undertaken. Significant variations in the conductivity of different polyaniline samples are also observed. The 10 min sample shows significantly enhanced conductivity as compared to the 20 min and 24 h. PANI samples having well defined nanofibers.

Electrical conductivity and dielectric properties of sulfamic acid doped polyaniline

The temperature and frequency dependence of dielectric constant (ε′) and dielectric loss (ε″) is studied for different samples of polyaniline (PANI), doped with different concentration of sulfamic acid in the frequency range (10–100 kHz) and temperature range (300–400 K). The dc conductivity has also been measured to see the effect of sulfamic acid and the conduction mechanism has been explained by the propagation of polaron through a conjugated polymer chain due to shifting of double bonds (alternation), which gives rise to electrical conduction.

BF3-doped polyaniline: A novel conducting polymer

We review the unusual structural, transport and magnetic properties of highly conducting polyaniline, doped with boron trifluoride. Our studies establish the unique conducting state of this system, which is in distinct contrast with the conventional proton-doped polyaniline samples.

Metallic transport in polyaniline

Despite nearly three decades of materials development, the transport properties in the 'metallic state' of the so-called conducting polymers are still not typical of conventional metals. The hallmark of metallic resistivity--a monotonic decrease in resistivity with temperature--has not been obtained at temperatures over the full range below room temperature; and a frequency dependent conductivity, sigma(omega), typical of metals has also not been observed. In contrast, the low-temperature behaviour of 'metallic' polymers has, in all previous cases, exhibited an increase in resistivity as temperature is further decreased, as a result of disorder-induced localization of the charge carriers. This disorder-induced localization also changes the infrared response such that sigma(omega) deviates from the prediction of Drude theory. Here we report classic metallic transport data obtained from truly metallic polymers. With polyaniline samples prepared using self-stabilized dispersion polymerization, we find that for samples having room-temperature conductivities in excess of 1,000 S cm(-1), the resistivity decreases monotonically as the temperature is lowered down to 5 K, and that the infrared spectra are characteristic of the conventional Drude model even at the lowest frequencies measured.

Synthesis of H2SO4 doped polyaniline film by potentiometric method

H2SO4 doped polyaniline films were synthesized in aqueous acidic media. The polyaniline film deposited on platinum electrode exhibits highest conductivity. The conductivity of each H2SO4 doped polyaniline sample was determined by the four-probe technique. The current-voltage curve exhibits that polyaniline sample has an ohmic behaviour. Experiments were conducted to establish the conductivity of the sample from room temperature to 110°C. The current was set constant. It has been observed that at lower current as well as higher current conductivity of the polyaniline sample is due to the electrons transferred to the conduction band. It is observed that the concentration ratio of 0.2:1 of aniline and H2SO4 for synthesis of PANI film on platinum electrode shows good conductivity.

Transport and magnetic properties of conducting polyaniline doped withBX3(X=F, Cl, and Br)

We report transport and magnetic properties of a different class of highly conducting polyaniline, doped with boron trihalides $\mathrm{B}{X}_{3}$ ($X=\mathrm{F}$, Cl, and Br). In order to understand the transport mechanism we analyze the temperature dependence of resistivity of a large number of samples, made by pelletizing doped polyaniline powder and by doping films of polyaniline. We find that the charge transport in this class of conducting polyaniline is driven by the charging-energy limited transport of charge carriers, in contrast to the quasi-one-dimensional variable range hopping conduction prevalent in conventional proton-doped polyaniline samples. Magnetic susceptibility provides further insight into the unusually high intrinsic conductivity behavior.