Polyaniline Emeraldine Salt Research Articles

A Scanning Kelvin Probe Investigation of the Interaction of PEDOT:PSS Films with Metal Surfaces

The study of conducting polymers (CPs) is of significant current interest due to their incorporation in a range of applications, including optical and electronic devices. Poly(3,4-Ethylenedioxythiophene)-Poly(Styrene Sulphonate) (PEDOT:PSS) is considered one of the most electrochemically and thermally stable CPs available at present 1. In many applications there is a requirement for electrical contact to be made between an organic PEDOT:PSS layer and a metallic substrate and therefore it highly important to understand the interaction between the CP and various metals, in order to gauge the long term stability of the metal-ICP interface. In this work an in-situ scanning Kelvin probe (SKP) technique is employed to measure the Volta potential differences of various PEDOT:PSS coated metal surfaces to identify instances where a reaction may be taking place at the buried interface. Previous studies have demonstrated the capability of SKP in elucidating the nature of the interaction of polyaniline and polypyrrole coatings with various metal surfaces 2- 4.Experiments have been carried out on a range of metals spanning a significant part of the electrochemical series. A threshold thickness of PEDOT:PSS of 3 μm was determined for more reactive metals (i.e. Ni, Zn, Al and Mg), at or above which a consistent Kelvin probe potential (EKP) value of ca. -0.15 V vs. SHE was measured. A potential of -0.4 V vs. SCE (ca. -0.156 V vs. SHE) has been reported previously by Ghilane et al, at which a PEDOT:PSS polymer film converts from the oxidized form to the reduced form 5. The constant value of -0.15V vs SHE measured for coated Ni, Zn, Al and Mg surfaces strongly suggests that these metals are polarized to this potential by a PEDOT:PSS(ox)/PEDOT:PSS(red) redox couple, where (ox) and (red) refer to the oxidized and reduced form of the CP respectively. This in turn implies that each of these metals enters into a galvanic interaction with the PEDOT:PSS, causing oxidation at the metal-coating interface and the reduction of a fraction of the CP.For a selection of more noble metals, (i.e. Pt, Ag and Cu) no consistent EKP values are observed (see Figure 1) and this is attributed to the fact that no redox reaction with PEDOT:PSS occurs. In such a case the PEDOT:PSS coating remains fully oxidised, resulting in potentials that are consistently higher than Eo(PEDOT:PSS(ox)) /(PEDOT:PSS(red)). The current investigation also demonstrates that cyclic re-oxidation of a PEDOT:PSS coating applied to a Al surface by atmospheric oxygen can occur. Previous studies have reported that sustained substrate ennoblement with other conducting polymers, such as Polyaniline emeraldine salt 2 occurs on ferrous metals by this mechanism. Upon removal of oxygen, EKP values measured for PEDOT:PSS coated Al decrease to ca. -0.38 V vs. SHE, a value similar to that that measured for uncoated Al. Upon the reintroduction of air, EKP values return to the values recorded initially. Therefore it seems that the presence of oxygen is important in maintaining the PEDOT:PSS redox state. Under conditions of low oxygen availability, complete reduction of PEDOT:PSS by the underlying Al is possible. This is confirmed by colorimetric observations of the thin PEDOT:PSS layer adherent to the Al surface.

Quartz crystal microbalance VOCs sensor based on dip coated polyaniline emeraldine salt thin films

Quartz crystal microbalance (QCM) technique has been used to detect a number of aromatic volatile organic compounds (VOCs) vapors widely used in research and industrial fields. Detection was based on dip coated polyaniline emeraldine salts (PANI-ES) thin films doped with three different acids, i.e. hydrochloric acid (HCl), dodecylbenzene sulfonic acid (DBSA) and 1,5-naphtalene disulfonic acids (1,5-NDSA)) on AT-cut 10MHz QCM electrode. Frequency change was recorded upon adsorption and desorption of (VOCs) on PANI films. It was found that frequency shifts varied linearly with both vapor concentration in part per million (ppm) and film thickness in nanometer (nm). Frequency changes are assumed to be mainly due to electrostatic interactions established between vapor molecules and dopant agents within PANI-ES films. Particularly, PANI-DBSA films were found to be highly sensitive (∼7Hz/ppm), selective to para-xylene (over toluene and benzene) and have a limit of detection of 3ppm. Interestingly, the films exhibit excellent recovery within less than 3min.

Temperature Dependent Electrical Properties of Green Synthesized Silver Nanoparticles-Polyaniline Composite

Polyaniline (PANI) Nanocomposites are potential materials for actuators, EMI shielding, Fuel cells and components in non volatile memory. Silver nanoparticles have wide range of applications such as catalysis, microelectronics, biotechnology and silver-oxide batteries. This work reports the effect of thermal alteration [lowhigh temperatur on the electrical conductivity of green synthesized silver (Ag) nanoparticles-polyaniline composite. A simple low cost green synthesis using Azadirachta indica [Neem] extract is employed for synthesis of silver nanoparticles; Polyaniline is prepared by redox polymerization of aniline using ammonium per sulphate. The silver nanoparticles are incorporated into Polyaniline during polymerization. PANI and PANI-Ag composites are characterized by FTIR, UV-Vis, TGA, XRD, TEM and DC conductivity. The DC conductivity and UV-Vis spectral response were recorded for the samples at low temperatures [263K, 273K, and 283 and high temperatures [353K, 433K, and 533. The effect of thermal alteration showed a significant change in both conductivity and UV-Vis spectral response. UV-visible spectra show the transition occurring in PANI Emeraldine salt phase to Pernigraniline with increase in temperature. TGA analysis confirms the improved thermal stability for PANI-Ag composite. The mechanism of electrical conductivity with temperature in the system is investigated and reported. Thus, this work deals with an approach to analyze the electrical behavior of green synthesized silver nanoparticles composited with a conducting polymer. The results show that these composites can be suitable for temperature dependent semiconductors, bio sensors and catalytic reactions.

Nanostructured Polyaniline Emeraldine-base form (EB-PANI): a structural investigation for different neutralization times

Polyaniline Emeraldine-base form (EB-PANI) was chemically obtained through the neutralization of Polyaniline Emeraldine-salt form (ES-PANI) using NaOH 0.5M at 3, 24 and 48h of neutralization. X-ray Diffraction (XRD), Le Bail Method, Small-angle X-ray Diffraction (SAXD), Small-angle X-ray Scattering (SAXS) and Scanning Electron Microscopy (SEM) were used to characterize the obtained polymers. EB-PANI crystal data obtained at 3h of neutralization were a=5.7230Å, b=17.7233Å, c=19.2336Å, α=85.2879°, β=84.6952° and γ=87.7014°. Crystallinity percentage was obtained using the XRD patterns and remained around 32% during the neutralization process. Le Bail Method revealed that the crystallites were very small lamellae with an oblate spherical shape and global average size around 33Å. By SAXS it was obtained the particle Radius of Giration (Rg) around 200Å. The maximum particle size (Dmax) of 550Å was obtained from the Pair-distance Distribution Function (p(r)). SEM images showed very small nanofibers morphology formed by interconnected nonhomogeneous nanospheres. EB-PANI electrical conductivity was 1.32×10−7S/cm along the neutralization process.

ESR properties of polyaniline in a wide pH range

In this paper, polyaniline was synthesized using cyclic voltammetry in a potential range between −0.20 and 1.10V (vs. SCE), in a solution consisting of 0.20M aniline and 0.60M H2SO4. The electron spin resonance (ESR) measurements of the emeraldine salt of polyaniline were done in a wide pH range of 0.7 (0.20M H2SO4 solution) to 12.0 of 0.30M Na2SO4 solution. It was found that the ESR signal of polyaniline was still very strong at pH 10.0 and then its ESR signal disappeared at pH>10.0. This result is unexpected because polyaniline was electrochemically inactive and its conductivity vanished at pH>5.0 based on the previous reports. The visible spectra of polyaniline showed no change in the absorption peak position in a pH range of 0.7–7.0, indicating no occurrence of deprotonation; while its absorption peak shifted markedly towards the short wavelength direction from pH 8.0 to 12.0, as a result polyaniline film become purple, indicating occurrence of deprotonation. The ESR signal disappearance and deprotonation of polyaniline are strongly related to pKb values of pH functional group in polyaniline chains. The entire deprotonation process of polyaniline is suggested to include the conventional deprotonation step, i.e.; without charge transfer and the reduction step of polyaniline that was confirmed with electrochemical measurements.

Conduction in polyaniline emeraldine salt in the terahertz region: A temperature dependence study

The temperature-dependent conductivity of polyaniline emeraldine salt (PAni-ES) was studied by terahertz (THz) time-domain spectroscopy from 80 to 290K to investigate conduction properties in the THz region. The absorption coefficient and index of refraction increase with temperature. This reflects an increasing conductivity, which indicates a thermally assisted hopping transition. The frequency-dependent behavior of the conductivity is described by using the Mott–Davis model. The model fitting parameter, S, decreases with increasing temperature, indicating a possible correlated barrier hopping mechanism. Lastly, the activation energy at THz frequencies decreases with increasing frequency, suggesting intraband transitions.

Interfacial Interactions of Polyaniline Grafted Alumina Hybrid

SummaryA new low solvent method of silylation followed by functionalization of oxide surfaces with polyaniline (PANI) was applied to alumina. The method comprises silylating alumina with 3‐(phenylaminopropyl)trimethoxysilane followed by grafting PANI onto the silylised surface by in situ polymerisation of aniline. A novel approach was developed for removal of PANI homopolymer formed as a by‐product was removed using 1(N)‐methyl‐2‐pyrrolidone (NMP)‐aliphatic amine binary solvent, which dedoped the emeraldine salt of PANI in a single, one‐pot procedure and made it soluble in NMP. After re‐doping with methanesulfonic acid the silylated alumina‐PANI hybrid became electrically conductive. The interfacial interactions within the hybrid material were investigated by several analytical techniques namely, elemental analysis, Fourier transform infrared spectroscopy, solid‐state 13C and 29Si nuclear magnetic resonance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy.

Inhibition of corrosion-driven organic coating delamination from a zinc surface using polyaniline pigments

In-coating dispersions of the para-toluene sulfonic acid emeraldine salt (ES) of polyaniline (PAni-pTS) are shown to be highly effective inhibitors of corrosion-driven organic coating delamination on zinc surfaces. However, this inhibition is achieved without the characteristic ennoblement of substrate potentials typically observed for ferrous metals. At high humidity, galvanic interaction of oxidizing PAni-pTS pigments with the underlying zinc causes the growth of an interfacial oxide film. The period of oxide growth coincides with the duration over which the Zn surface is temporarily ennobled by the PAni-pTS. The results of experiments designed to elucidate the inhibition mechanism are presented, where substrate potentials, along with delamination and oxide growth kinetics are compared with equivalent in-coating compositions of ES and emeraldine base (EB). It is demonstrated that the basic nature of the interfacial oxide layer causes PAni-pTS re-oxidation to the non-conducting EB form, accounting for the loss of ennoblement. Efficient inhibition is achieved by a combination of a PAni-pTS-induced oxide layer and a zinc para-toluene sulfonate phase, acting as a reservoir of underfilm Zn2+ ions, producing a suppression of cathodic oxygen reduction. Availability of Zn2+ ions at the organic coating–metal interface both reinforces and prevents the dissolution of the amphoteric zinc oxide surface layer.

Inkjet Printed Negative Supercapacitors: Synthesis of Polyaniline‐Based Inks, Doping Agent Effect, and Advanced Electronic Devices Applications

Low frequency negative supercapacitors and high frequency negative capacitors are realized developing a polyaniline (PANI) based ink for piezoelectric inkjet printers, water based. PANI is synthesized by oxidation polymerization starting from the aniline dimer, thus avoiding the use of a toxic/mutagen substance such as aniline. In order to work in aqueous phase, the reverse addition of the dimer in the oxidative solution is made. The chlorinated emeraldine salt of PANI is produced and emeraldine base is prepared by dedoping. Two different doped PANI solutions are produced by solubilization of the emeraldine salt in dimethylsulphoxide and addition of respectively trifluorosulfonic acid and camporsulfonic acid, and then used as inks for the fabrication of inkjet‐printed tracks of different geometries. The properties of inkjet‐printed devices are characterized both in DC and AC regimes, showing very good performances under specific measurement conditions in terms of conductivity, as well as extremely interesting phenomena whose origin is still under debate, such as low frequency negative supercapacitance, high frequency negative capacitance and negative resistance. The realization of the highest negative supercapacitance realized so far, of –2.3 mF @ 30 Hz, corresponding to a specific mass capacity of –799 F g−1, is reported.

Poloxamer and gelatin gel guided polyaniline nanofibers: synthesis and characterization

A rapid polymerization technique was successfully employed to synthesize interconnected polyaniline (PANI) nanofibers using chemical oxidative polymerization inside a soft template. The thermoreversible hydrogels of Lutrol F 127 and gelatin were used as templates where the interstices present in the hydrogel were responsible for the formation of PANI nanofibers with a diameter in the range ca 70−75 nm and ca 50−55 nm respectively and several micrometers in length. The doped emeraldine salt of PANI was confirmed by Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy. The crystallinity of as-synthesized PANI nanofibers for both cases was verified by an X-ray diffraction study while thermogravimetric analysis was performed to compare the relative stability of the synthesized PANI nanofibers. The electrical conductivities of polymerized PANI are of the order of 10−3 S cm−1 and are compared with those of template fabricated PANI. The Lutrol F 127 gel guided PANI nanofibers showed a rectifying property while the gelatin gel guided PANI provided a simple ohmic nature. © 2013 Society of Chemical Industry

Structural and electrical characterization of polyanilines synthesized from chemical oxidative polymerization via doping/de-doping/re-doping processes

Structural characterization of various emeraldine salt (ES) and emeraldine base (EB) polyaniline (PANI) powders synthesized from chemical oxidative polymerization and then via de-doping and re-doping processes is first presented. Partial crystallinity with well-separated x-ray diffraction peaks is observed in the as-prepared ES PANI powder and an amorphous characteristic is identified in the de-doped EB PANI powder. From scanning electron microscopy, both the nanostructures of the as-prepared ES and de-doped EB PANI precipitated powders possess similar morphology. This finding reveals that the de-doping process to remove the counter-ions intercalated between the as-prepared ES PANI chains makes the de-doped EB PANI pieces become soft but does not change the nanostructures significantly. Then, the electrical conductivity perpendicular to the surface of the pressed PANI disc pellets is studied. The re-doped ES PANI pellets possess less electrical conductivity than their as-prepared counterparts, which suggests that during the re-doping process the counter-ions (Cl− or ) are re-adsorbed predominantly on the surface region of the PANI nanostructures. Besides, the re-doping of larger counter-ions (with respect to Cl−) intercalated between the PANI chains increases the d-spacing of (1 0 0) planes and hence reduces the corresponding π–π inter-chain interaction. Finally, from the temperature dependence of the electrical conductivity together with the structural information, the charge carrier hopping mechanisms perpendicular to the surface of the pressed pellets corresponding to various PANI samples are compared and discussed.

DFT Study of Polyaniline NH3, CO2, and CO Gas Sensors: Comparison with Recent Experimental Data

Density functional theory studies (DFT) have been carried out to evaluate the ability of polyaniline emeraldine salt (PANI ES) from 2 to 8 phenyl rings as sensor for NH3, CO2, and CO. The sensitivity and selectivity of nPANI ES among NH3, CO2, and CO are studied at UB3LYP/6-31G(d) level of theory. Interaction of nPANI ES with CO is studied from both O (CO(1)) and C (CO(2)) sides of CO. Interaction energy, NBO, and Mulliken charge analysis were used to evaluate the sensing ability of PANI ES for different analytes. Interaction energies are calculated and corrected for BSSE. Large forces of attraction in nPANI ES-NH3 complexes are observed compared to nPANI ES–CO2, nPANI ES-CO(1), and nPANI ES-CO(2) complexes. The inertness of +C≡O– in nPANI ES-CO(1) and nPANI ES-CO(2) complexes are also discussed. Frontier molecular orbitals and energies indicate that NH3 changes the orbital energy of nPANI ES to a greater extent compared to CO2, CO(1), and CO(2). Peaks in UV–vis and UV–vis–near-IR spectra of nPANI ES are ...

Microcantilever sensors coated with doped polyaniline for the detection of water vapor

In the present work, PANI (polyaniline) emeraldine salt (doped) and base (dedoped) were used as the sensitive layer of a silicon microcantilever, and the mechanical response (deflection) of the bimaterial (coated microcantilever) was investigated under the influence of humidity. PANI in the emeraldine base oxidation state was obtained by interfacial synthesis and was deposited on the microcantilever surface by spin-coating (dedoped). Next, the conducting polymer was doped with 1 M HCl (hydrochloric acid). A four-quadrant AFM head with an integrated laser and a position-sensitive detector (AFM Veeco Dimension V) was used to measure the optical deflection of the coated microcantilever. The deflection of the coated (doped and undoped PANI) and uncoated microcantilever was measured under different humidities (in triplicate) at room pressure and temperature in a closed chamber to evaluate the sensor's sensitivity. The relative humidity (RH) in the chamber was varied from 20% to 70% using dry nitrogen as a carrier gas, which was passed through a bubbler containing water to generate humidity. The results showed that microcantilevers coated with sensitive layers of doped and undoped PANI films were sensitive (12,717 ± 6% and 6,939 ± 8%, respectively) and provided good repeatability (98.6 ± 0.015% and 99 ± 0.01%, respectively) after several cycles of exposure to RH. The microcantilever sensor without a PANI coating (uncoated) was not sensitive to humidity. The strong effect of doping on the sensitivity of the sensor was attributed to an increased adsorption of water molecules dissociated at imine nitrogen centers, which improves the performance of the coated microcantilever sensor. Moreover, microcantilever sensors coated with a sensitive layer provided good results in several cycles of exposure to RH (%).

Iodine vapor doped polyaniline nanoparticles counter electrodes for dye-sensitized solar cells

In this study, we demonstrated the enhanced efficiency of dye-sensitized solar cells (DSSCs) using iodine vapor-doped nanostructured polyaniline (PANI)-based counter electrodes (CEs). The electrical conductivities of chemically synthesized PANI emeraldine salt (PANI-ES) and dedoped emeraldine base (PANI-EB) were increased from 3.1Scm−1 to 9.3Scm−1 and 2.0×10−5Scm−1 to 0.5Scm−1, and the doping levels of those were increased from 38.2% to 41.8% and 3.2% to 33.3%, respectively, via iodine vapor doping. Compared with PANI-ES and PANI-EB CEs, iodine-doped PANIs (PANI-ES-I2 and PANI-EB-I2) CEs with improved electrical properties were demonstrated higher electro-catalytic activity toward I−/I3− redox couples, due to better charge carrier transport and reduced charge transfer resistance. The cells based on the PANI-ES-I2 and PANI-EB-I2 CE exhibited higher photovoltaic parameters and efficiency. Moreover, we successfully increased the cell efficiency of the PANI-ES-I2 CE-based DSSCs to a maximum efficiency of ~7.86%.

폴리아닐린 나노섬유를 이용한 광경화형 전도성 투명필름의 제조 및 특성

폴리아닐린(PANI) 나노섬유를 전도성 충전제로 사용하여 광경화형 전도성 투명필름을 제조하였다. 화학산화중합(chemical oxidation polymerization)으로 나노섬유 구조의 산화형 폴리아닐린(ES-PANI)을 합성하였다. ES-PANI는 디도핑을 통해 환원형 폴리아닐린(EB-PANI)으로 유도하였다. 이것을 전도성 충전제의 전구체로 사용하여 도데실벤젠설폰산(DBSA)이 포함되어 있는 광경화형 레진에 분산시키면 재도핑된 재산화형 폴리아닐린(rES-PANI)을 얻을 수 있었다. 이런 과정을 통해 나노섬유 형태가 유지되면서 높은 전도성과 분산안정성이 우수한 광경화형 전도성 레진용액을 제조할 수 있었다. 제조된 광경화형 전도성 레진용액은 상온에서 3달 정도 두어도 rES-PANI 충전제의 침전물이 생기지 않았다. 또한 이 용액을 폴리(메틸 메타크릴레이트)(PMMA) 기재 위에 스핀코팅 후 광경화하여 약 <TEX>$5{\mu}m$</TEX> 두께의 전도성 투명필름을 제조하였다. rES-PANI 나노섬유 농도가 1.4 wt%일 때 표면저항 <TEX>$6.5{\times}10^8{\Omega}/sq$</TEX>, 550 nm 파장에서 91.1%의 투과도를 보였다. ES-PANI의 디도핑-재도핑(dedoping-redoping) 과정을 통해 광경화형 전도성 레진용액에 분산된 PANI는 농도에 따라 필름표면저항과 광학적 투명도를 조절할 수 있는 대전방지 보호필름을 제작하는 새로운 방법을 제시하였다. Conductive polyaniline (PANI) nanofibers in UV-curable resin were used for a transparent conductive film. The emeraldine-salt PANI (ES-PANI) nanofibers were prepared by chemical oxidation polymerization of aniline, which could be changed into emeraldine-base PANI by dedoping. EB-PANI nanofibers as a precursor for conductive fillers were thereby transformed into re-dpoed PANI (rES-PANI) by dodecylbenzenesulfonic acid in the UV-curable resin solution. rES-PANI nanofibers have high conductivity and long-term stability in the solution without a defect of nanostructure. The resulting conductive resin solution was proved to be highly stable where no precipitation of rES-PANI fillers was observed over a period of 3 months. The transparent film was spin-casted on a poly(methyl methacrylate) sheet of thickness ca. <TEX>$5{\mu}m$</TEX>. A surface resistance of <TEX>$6.5{\times}10^8{\Omega}/sq$</TEX> and transmittance at 550 nm of 91.1% were obtained for the film prepared with a concentration of 1.4 wt% rES-PANI nanofibers in the solution. This transformation process of rES-PANI from ES-PANI by dedoping-redoping can be an alternative method for the preparation of an antistatic protection film with controllable surface resistance and optical transparencies with the PANI concentration in UV-curable solution.

Chemical modification of nano-structured polyaniline by N-grafting of hexadecylbromide

This study aims to explore an effective route for the preparation of conductive N-substituted polyaniline by incorporation of hexadecyl side chains into the fully reduced form of nano-structured polyaniline leucoemeraldine base. For this purpose, at first nano-structured emeraldine salt polyaniline was synthesized by interfacial chemical oxidative polymerization. The dark green product salt was neutralized by an ammonia solution in order to give us an emeraldine base (EB). Thereafter, the reduced form of nano-structured polyaniline was prepared by treating the obtained EB with phenylhydrazine in methanol. The excess amount of butyllithium was applied to abstract protons from the amine nitrogens of nano-structured LEB polyaniline chains. Thereafter, deprotonated polyaniline was reacted with hexadecylbromide to prepare poly(N-hexadecylaniline) through N-grafting reaction. The obtained poly(N-hexadecylaniline) was characterized using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry, and thermal gravimetry analysis (TGA). The average diameters of unsubstituted and substituted polyaniline particles were determined by particle size analyzer. The optical properties of the poly(N-hexadecylaniline) in the undoped and doped state were obtained using UV–vis spectroscopy and the electrical conductivity of the sample was measured using sample in which the conductive materials were sandwiched between two Ni electrodes at room temperature. Also, electroactivity of the synthesized polymer was investigated under cyclic voltammetric conditions on the surface of the working glassy carbon electrode. The solubility of the obtained polymer was examined in common organic solvents.

Spectroscopic Studies of Nano Size Crystalline Conducting Polyaniline

Polyaniline (PANI) was synthesized in Emaraldine form by in situ chemical oxidation method by using Ammonium perdisulphate as oxidizing agent. The XRD pattern indicates that PANI is a semi crystalline solid with d-spacing 4.801 Ǻ and 4.358 Ǻ. The SEM results show that the particle size lies as an average of 80 nm and length 550nm. Similarly the UV-Visible spectra of this polymer indicate two absorption bands at around 320nm and 640nm. These absorption bands are attributed to the transitions of π → π* and Benzenoid to Quinoid respectively. The FT-IR spectrum of PANI shows strong bands at 3442, 2925, 1598, 1494, 1453, 1176, 1112 and 744 cm -1 respectively. 1 H NMR spectrum shows 6 peaks with chemical shifts δ = 7.452, 7.468, 7.505, 7.525, 7.604, 7.638 ppm. The lower three peaks at (δ = 7.452, 7.468, 7.505 ppm) are attributed to the protons related to the 14 N nucleus. These spectral lines intensity ratio lies as 1:1:1. Another three peaks at (δ = 7.525, 7.604, 7.638 ppm) are attributed to the three protons, which are present at CH Benzenoid, NH, CH at Quinoid. The intensity ratio of these spectral lines is 1:2:1. The room temperature ESR spectrum of PANI Emeraldine salt shows an unresolved peak with lande's g factor 2.010 due to polaron.

Evaluation of an environmentally friendly anticorrosive pigment for alkyd primer

An alkyd formulation containing zinc phosphate (10wt.%) was prepared and subsequently modified replacing the latter anticorrosive additive by a very low concentration of conducting polymer. Specifically, three modified paints, which contain polyaniline emeraldine base (undoped form), polyaniline emeraldine salt (doped form) and an eco-friendly polythiophene derivative (partially oxidized), were formulated. The properties and corrosion resistance of the four alkyd coatings have been characterized. Among the three modified paints, the one containing polythiophene shows the best adherence and the highest corrosion resistance. This has been attributed to the fact that the miscibility of the polythiophene derivative with the alkyd formulation is better than that of polyaniline. Furthermore, accelerated corrosion assays and electrochemical impedance spectroscopy measurements revealed that the corrosion resistance of the paint with polythiophene is several orders of magnitude higher than that with zinc phosphate. The polythiophene derivative has been found to induce the formation of a passivating and well-adhered layer between the coating and the surface, preventing the access of chloride anions and oxygen to the substrate.

Electrochemical properties of leucoemeraldine, emeraldine, and pernigraniline forms of polyaniline/multi-wall carbon nanotube nanocomposites for supercapacitor applications

We report on the synthesis and electrochemical properties of leucoemeraldine base, emeraldine salt and pernigraniline base forms of polyaniline (PANI) in the form of nanocomposites with MWNTs. The oxidation state of PANI in the composite is controlled by doping and dedoping of the emeraldine salt form of PANI/MWNT composite, which is prepared through chemical polymerization, using oxidizing and reducing agents without changing the morphology of PANI in the composite and is confirmed by ultraviolet–visible spectroscopy (UV–vis) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical and pseudocapacitive properties of the composites are investigated using cyclic voltammetry and analyzed with respect to the oxidation state of polyaniline. The PANI/MWNT nanocomposites show specific capacitance values of 217 F g −1, 328 F g −1 and 139 F g −1 for leucoemeraldine base, emeraldine salt and pernigraniline base, respectively. Electrochemical impedance spectroscopy is performed to explain the different electrochemical properties of PANI in different oxidation states.

Effects of temperature and humidity on electrospun conductive nanofibers based on polyaniline blends

This study focuses and discusses the effects of temperature and humidity on electrospun conductive nanofibers, made with different polymer blends, deposited directly on interdigitated electrodes. The selected conductive polymers were based on blends of polyaniline emeraldine salt form and three different carrier hosting polymers: polyvinilpyrrolidone, polystyrene, and polyethylene oxide respectively. The obtained fibrous layers were investigated by the electrical measurements and morphological analysis (scanning electron microscopy). The study was made on the correlation between the electrical changes and morphological discrepancies due to temperature treatment. Moreover, this article reports the effects of relative humidity variations on electrical parameters. Since polyaniline is a well-known sensing material for different gases and volatile organic compounds, this study could be considered a supportive study for employing of the mentioned polymer blends as chemical interactive materials in gas sensor applications.