Emeraldine Base Form Of Polyaniline Research Articles

Assembly of Conductive Polyaniline Microstructures by a Laser-Induced Microbubble.

Micropatterns of conductive polymers are key for various applications in the fields of flexible electronics and sensing. A bottom-up method that allows high-resolution printing without additives is still lacking. Here, such a method is presented based on microprinting by the laser-induced microbubble technique (LIMBT). Continuous micropatterning of polyaniline (PANI) was achieved from a dispersion of the emeraldine base form of PANI (EB-PANI) in n-methyl-2-pyrrolidone (NMP). A focused laser beam is absorbed by the EB-PANI nanoparticles and leads to formation of a microbubble, followed by convection currents, which rapidly pin EB-PANI nanoparticles to the bubble/substrate interface. Micro-Raman spectra confirmed that the printed patterns preserve the molecular structure of EB-PANI. A simple transformation of the printed lines to the conducting emeraldine salt form of PANI (ES-PANI) was achieved by doping with various acid solutions. The hypothesized deposition mechanism was verified, and the resulting structures were characterized by microscopic methods. The microstructures displayed conductivities of 3.8 × 10-1 S/cm upon HCl doping and 1.5 × 10-1 S/cm upon H2SO4 doping, on par with state-of-the-art patterning methods. High fidelity control over the width of the printed lines down to ∼650 nm was accomplished by varying the laser power and microscope stage velocity. This straightforward bottom-up method using low-power lasers offers an alternative to current microfabrication techniques.

Synthesis of polyaniline-modified graphene oxide for obtaining a high performance epoxy nanocomposite film with excellent UV blocking/anti-oxidant/ anti-corrosion capabilities

This paper focuses on the synthesis and modification of graphene oxide nanosheets with polyaniline. The main aim is to take the advantages of both graphene oxide and polyaniline in enhancing the long-term performance (including weathering and corrosion) of exterior nanocomposites. For this purpose, the synthesized graphene oxide was treated via an in-situ polymerization process. The modified hybrid nanosheets were characterized by Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction analysis (XRD), Ultraviolet–visible spectrophotometry (UV–Vis) and Raman spectroscopy. It was approved that the emeraldine base form of polyaniline has been successfully polymerized on the graphene oxide nanosheets in two forms of non-covalent bonding through π-π interactions between quinoid ring of PANI and basal plane of graphene oxide, and covalent bonding through reaction with epoxide group. The modified nanosheets were introduced into a typical epoxy matrix and then subjected to accelerated weathering and corrosion cycles. The results revealed that a considerable improvement in both weathering (42% reduction in ΔE) and corrosion resistance was achieved which was mainly attributed to the considerable enhancement in UV shielding, radical scavenging as well as better dispersion of graphene oxide modified with polyaniline.

Adsorption and reduction: combined effect of polyaniline emeraldine salt for removal of Cr(VI) from aqueous medium

In this study, we have reported the removal of Cr(VI) ions by polyaniline (PANI) particles from aqueous medium. PANI in its emeraldine salt (ES) form can interact with Cr(VI), which is present as \(\text {HCrO}_{\text {4}}^{\boldsymbol {-}} \) in two ways. The adsorption of \(\text {HCrO}_{\text {4}}^{\boldsymbol {-}} \) ions due to the electrostatic interaction between partially positively charged PANI backbone and Cr(VI) anions causes the major portion of Cr(VI) removal and a small portion of Cr(VI) is reduced to Cr(III) by PANI (ES). The adsorption follows Langmuir adsorption isotherm and second-order kinetic model. It is observed that the removal of Cr(VI) is negligibly effected by the presence of other anions in the aqueous medium. The adsorption capacity of PANI (ES) is found to be 123 mg g−1, which is very high compared to activated carbon-based materials. The adsorbed anions can be desorbed by converting PANI emeraldine salt (ES) to PANI emeraldine base (EB). The EB form of PANI can be converted into ES form by treating with acid, which can be reused as adsorbent. It is important to note that the PANI (ES) is oxidized by \(\text {HCrO}_{\text {4}}^{\boldsymbol {-}} \) ions which decrease the hydrophilicity of the surface of PANI particles. This causes the decrease in adsorption capacity of recycled PANI.

Preparation and characterization of a new polyaniline salt with good conductivity and great solubility in dimethyl sulfoxyde

In this study, we propose a novel conducting and soluble polyaniline salt prepared by chemical polymerization in the presence of new doping agent (IAs). This last is prepared by sulphonation of itaconic acid (IA) with concentrated sulphuric acid in THF. The obtained doped polyaniline (PANI-IAs) is extremely soluble in dimethyl sulfoxyde (DMSO) at room temperature, in which the solubility reach 44 mg mL-1. The conductivity measurement of doped polyaniline powder precipitated in THF as dispersing medium gave a value of 0.13 S cm-1 when the emeraldine base form of polyaniline is fully protonated. The polyaniline salt sample is characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction, UV-Visible spectra and FTIR spectra.

Development of Electrospun Polyaniline/ZnO Composite Nanofibers for LPG Sensing

In this paper we report the highly sensitive at low temperature and low concentration of liquefied petroleum gas (LPG) sensor based on D-Camphor-10-Sulphonic acid (CSA) doped Polyaniline/Polyethylene Oxide (PANI/PEO) and PANI/ZnO/PEO nanofibers fabricated by electrospinning technique. Nano-sized particles of zinc oxide (ZnO) were synthesized using sol-gel method. The emeraldine base form of polyaniline (PANI) and PANI/ZnO synthesized by chemical oxidative polymerization were treated with CSA for better solubility and conductivity and then blended with PEO solution to get nanofibers using electrospinning. The morphology and structure of electrospun nanofibers of CSA doped PANI/PEO and PANI/ZnO/PEO were investigated by SEM, UV-VIS, FTIR and XRD. The change in electrical resistance of CSA doped PANI/PEO and PANI/ZnO/PEO for 1000ppm of LPG was measured. Both the samples showed a rapid and reversible resistance change upon exposure to LPG gas at 1000ppm concentration. Maximum sensitivity was achieved at 36°C for PANI/ZnO/PEO indicating suitability of nanofibrous PANI/ZnO/PEO towards LPG sensing as compared to pure ZnO and PANI.

Time resolved excitation dynamics in emeraldine base

Using femtosecond pump–probe transient absorption spectroscopy (wavelengths 330–800nm), we observed and explained excited state, charge transfer and polaron state dynamics in emeraldine base form of polyaniline in dimethyl sulfoxide solution. The excited state created by a pump pulse (700nm) in the quinoid absorption Q-band loses its initial symmetry by subsequent energy transition to a charge transfer state within 50fs. The hot charge transfer state either recombines non-radiatively into the ground state with decay time constant 0.55ps or transfers into a relaxed state corresponding to the relaxed phenyl geometry during ca 2.1ps. This relaxed state shows a prolonged lifetime of about 6.5ps before its recombination to the ground state. However, a small amount of long-lived polarons with lifetime of about 2ns in air and with lifetime longer than 6ns in the solution bubbled with dry N2 was detected.

A facile method for the sensing of antioxidants based on the redox transformation of polyaniline

Polyaniline (PANI) is one of the most studied conducting polymers. It could adopt a number of chemical forms depending on the redox states of the assay solution. It was observed that the emeraldine base form of PANI could be reduced by common antioxidants (such as glutathione and ascorbic acid), which resulted in clear changes of the solution color and the UV–vis absorption spectra. In addition, it was observed that the fluorescence of CdTe quantum dots could be efficiently quenched by PANI, and the fluorescence quenching could not take place by the addition of antioxidants. The intensity of the quantum dots fluorescence could be directly related to the amount of antioxidant added to the assay solution, thus a sensitive fluorescent turn-on sensor for antioxidant was established. The detection limits for glutathione and ascorbic acid were estimated to be 50nM and 100nM, respectively. Our assay is simple, sensitive, and label-free, we envision it could facilitate the antioxidant sensing related applications.

Emeraldine Base Form of Polyaniline Nanofibers as New, Economical, Green, and Efficient Catalyst for Synthesis of Z-Aldoximes

A facile, clean, economical, efficient, and green process was developed for the preparation of Z-aldoximes at room temperature under solvent-free condition using emeraldine base form of polyaniline as novel catalyst. In this methodology, PANI base absorbed the by-product of HCl (polluting chemical) from hydroxylamine hydrochloride and converted to polyaniline-hydrochloride salt (PANI-HCl salt). This PANI-HCl salt could be easily recovered and used in new attempts without any purification in many areas such as catalyst, electrical and electronics applications meant for conducting polymers. As far as our knowledge is concerned, emeraldine base as catalyst in organic synthesis for the first time.

Enhanced pH stability of conducting polyaniline by reprotonation with perfluorooctanesulfonic acid

Electrically conducting polyaniline (PANI) films have been prepared by reprotonation of the emeraldine base form of PANI with perfluorooctanesulfonic acid (PFOS). The reprotonated PANI-PFOS films have been characterized by UV–vis spectroscopy, water contact angle and electrical conductivity measurements. We report that reprotonation of PANI base with PFOS increased the water contact angle from 25° to 105°. The hydrophobic PANI-PFOS maintained a good level of conductivity even at pH=8 (σ=1.0×10−2Scm−1) whereas the PANI hydrochloride lost its conductivity at this pH (σ=5.0×10−9Scm−1). Long-term stability tests showed that the reprotonated PANI-PFOS film remained in its conducting form for three month.

Synthesis, characterization and electrorheological effect of sulfosalt‐type liquid‐crystalline ionomers containing polyaniline units

ABSTRACTA series of main‐chain liquid‐crystalline polymers (LCPs) with pendant sulfonic acid groups have been synthesized by use of biphenyl‐4,4′‐diol, 6,7‐dihydroxynaphthalene‐2‐sulfonic acid, and bis(4‐(chlorocarbonyl)phenyl) decanedioate in a one‐step esterification reaction. Emeraldine base form of polyaniline (PAN) is doped by the synthesized sulfonic acid‐containing LCPs to obtain PAN–LCP ionomers. A series of electrorheological (ER) fluids are prepared using the synthesized PAN–LCP ionomers and silicone oil. The chemical structure, liquid‐crystalline behavior, dielectric property of LCPs, and PAN–LCP ionomers, and ER effect of the ER fluids are characterized by use of various experimental techniques. The synthesized sulfonic acid‐containing LCPs and PAN–LCP ionomers display nematic mesophase. The PAN–LCP ionomers show a slight elevation of glass transition temperatures and decrease of enthalpy changes of nematic–isotropic phase transition compared with corresponding sulfonic acid‐containing LCPs. The relative permittivity of the PAN–LCP ionomers is much higher than that of the corresponding sulfonic acid‐containing LCPs. The ER effect of the PAN–LCP ionomer dispersions is better than PAN dispersions, suggesting a synergistic reaction should be occurred among liquid crystalline component, and PAN part under electric fields. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3395–3403, 2013

Exciton peak redshifting and broadening in polyaniline chains during ion-induced hydrophobic collapse and aggregation

The ion-induced reprecipitation of the emeraldine base form of polyaniline from an aqueous-organic binary solution is a facile method for obtaining polymer nanoparticles and microscale clusters. The hydrophobic collapse and aggregation that accompanies the addition of various cosolutes induces changes in the peak wavelength and linewidth of the main exciton absorption. In particular, we find that the addition of ionic cosoutes leads to a redshifting and broadening of this spectroscopic feature, with divalent coions exhibiting an additional hypsochromic reversal at high concentrations. The denaturant urea, in contrast, causes a blueshift and line-narrowing at all concentrations. Using a quantitative Lorentz fit, we show how the redshifting and broadening of this spectral feature can be attributed, at least in part, to the forced planarization of the polymer chains in the collapsed state.

Reduction of Emeraldine Base Form of Polyaniline by Pillar[5]arene Based on Formation of Poly(pseudorotaxane) Structure

We report on the reduction of polyaniline (PANI) by pillar[5]arene based on the formation of the poly(pseudorotaxane) structure. When pillar[5]arene was mixed with emeraldine base (EB) form of PANI, a blue solution color resulting from the EB form of PANI was diluted over time, and became completely colorless after 180 min. The FT-IR spectrum of the mixture of the EB form of PANI and pillar[5]arene displayed a new band at 1646 cm–1, which was assigned the C═O stretching band of benzoquinone. These results indicate that both oxidation of the hydroquinone units of pillar[5]arene and reduction of the EB form of PANI were induced by mixing the EB form of PANI and pillar[5]arene. Pillar[5]arene showed a stronger reducing ability than the unit model of hydroquinone. The ROE correlations between the methylene bridge protons of pillar[5]arene and the benzene protons of PANI indicated that the PANI chain was included into the pillar[5]arene cavity. Formation of the poly(pseudorotaxane) structure between PANI and p...

A hydrogen peroxide sensor based on a horseradish peroxidase/polyaniline/carboxy-functionalized multiwalled carbon nanotube modified gold electrode

We have developed a polyaniline/carboxy-functionalized multiwalled carbon nanotube (PAn/MWCNTCOOH) nanocomposite by blending the emeraldine base form of polyaniline (PAn) and carboxy-functionalized multiwalled carbon nanotubes (MWCNT) in dried dimethyl sulfoxide (DMSO) at room temperature. The conductivity of the resulting PAn/MWCNTCOOH was 3.6 × 10 −3 S cm −1, mainly as a result of the protonation of the PAn with the carboxyl group and the radical cations of the MWCNT fragments. Horseradish peroxidase (HRP) was immobilized within the PAn/MWCNTCOOH nanocomposite modified Au (PAn/MWCNTCOOH/Au) electrode to form HRP/PAn/MWCNTCOOH/Au for use as a hydrogen peroxide (H 2O 2) sensor. The adsorption between the negatively charged PAn/MWCNTCOOH nanocomposite and the positively charged HRP resulted in a very good sensitivity to H 2O 2 and an increased electrochemically catalytical current during cyclic voltammetry. The HRP/PAn/MWCNTCOOH/Au electrode exhibited a broad linear response range for H 2O 2 concentrations (86 μM–10 mM). This sensor exhibited good sensitivity (194.9 μA mM −1 cm −2), a fast response time (2.9 s), and good reproducibility and stability at an applied potential of −0.35 V. The construction of the enzymatic sensor demonstrated the potential application of PAn/MWCNTCOOH nanocomposites for the detection of H 2O 2 with high performance and excellent stability.

Photoinduced protonation of polyaniline assisted by hydrogen-bonding materials

Composites of the emeraldine base form of polyaniline (PANI-EB) and photo-acid generators (PAGs) increase their conductivities upon photo-irradiation due to protonation of PANI-EB. Such materials may be utilized to fabricate conducting patterns by photo-irradiation. However, the conductivity obtained by direct irradiation of PANI-EB/PAG composites was normally quite low, and conductivity above 10 −3 S cm −1 often required post-treatment with HCl. In this work, poly(vinyl alcohol) (PVA), which can form a hydrogen bonding network, was added to PANI-EB/PAG. Results showed that PVA enhanced film quality, conductivity and reproducibility. Photo-induced conductivity of 10 −2 S cm −1 was obtained when the ratio of PANI-EB/PVA/PAG was 1:1:0.6. A novel PAG, bis(p-hydroxyphenyl)phenylsulfoniumtriflate [(PhOH) 2PhS + OTf −], which can form hydrogen bonds with PANI was synthesized and mixed with PANI-EB. A composite of PANI-EB and the PAG with a ratio of 1:0.5 achieved a conductivity of 10 −1 S cm −1 after irradiation. However, the initial conductivity before irradiation was as high as 10 −5 S cm −1 due to relatively high acidity of the PAG.

Preparation of polyaniline asymmetric hollow fiber membranes and investigation towards gas separation performance

In this study, integrally skinned asymmetric hollow fiber membranes have been developed from emeraldine base form of polyaniline (PAni) for gas separation. High molecular weight PAni was synthesized in-house to provide the fresh supply of the polymer. The hollow fiber membranes were prepared using dry-jet wet spinning and the effects of air-gap distance on nascent fiber morphology, their gas permeation and mechanical properties were investigated. The spin-line stresses resulted in the molecular orientation of the polymer which had synergistic effect towards improving the gas performance of the PAni hollow fiber membranes. The induced molecular orientation also resulted in improvement in mechanical properties of the hollow fiber membrane. The use of volatile co-solvent, tetrahydrofuran (THF) assisted in the skin layer formation which showed a substantial improvement in the gas permeation performance of the hollow fiber as the time of evaporation was varied. Present PAni based hollow fibers showed a selectivity of 10.2 for O 2/N 2, 105.6 for H 2/N 2 and 7.9 for H 2/CO 2 with the H 2 and O 2 permeance of about 5.0 and 0.49 × 10 −6 cm 3 (STP)/cm 2 s cmHg, respectively.

Layered nanostructures of polyaniline with graphene oxide as the dopant and template

Novel layered structures of polyaniline (PANI) doped with graphene oxide (GO) were directly prepared by adding GO aqueous solution into the emeraldine base form of PANI (PANI-EB) dissolved in a mixture solution of m-cresol and ethanol. The method is simple and inexpensive because of saving inorganic or organic acids as the dopant, opening a new way to prepare hybrid materials of PANI with GO. It was proposed that the π–π planar structure of GO and the carboxyl groups on the surface of GO are served as the template and dopant, respectively that results in the formation of the layered structures. The doping function of GO in the PANI-GO has been proved by structural characterizations and conductivity measured by a four-probe method.

Enzyme Entrapment in Reprecipitated Polyaniline Nano- and Microparticles

We introduce a novel method for fabricating nano- and microscale polyaniline particles containing an entrapped oxidoreductase enzyme for use in biosensing applications. This facile process utilizes the reprecipitation of the emeraldine base form of polyaniline from an aqueous−organic suspension, with hydrophobic collapse and subsequent cross-linking of the polymer induced by adjusting the ionic strength beyond a critical threshold. We present UV−vis spectroscopy data, including a quantitative treatment of the spectral line width, along with dynamic light scatting results, to explain the conformation changes in the polyaniline chains that accompany this transition. The resultant aggregated supermolecular polyaniline formations immobilize enzymes via gelation entrapment, augmented by electrostatic attraction, without the need for harsh reaction conditions or additional reagents. Because of its strong optical features at visible wavelengths that can serve as probes for chain conformation, oxidation state, and protonation level, polyaniline may act as a model system for the study of hydrophobic and ion screening effects in proteins and other foldamers.

The role of oxygen in the interaction of emeraldine base polyaniline with Cu(II) or Fe(III) ions in NMP solution

The influence of molecular oxygen in the interactions of emeraldine base form of polyaniline (EB-PANI) with Fe(III) or Cu(II) ions in 1-methyl-2-pyrrolidinone (NMP) solutions has been investigated by UV–vis–NIR, resonance Raman and electron paramagnetic resonance (EPR) spectroscopies. Through the set of spectroscopic results it was possible to rationalize the role of O 2 and to construct a scheme of preferential routes occurring in the interaction of EB-PANI with Fe(III) or Cu(II). Solutions of 4.0 mmol L −1 EB-PANI with 0.8, 2.0 and 20 mmol L −1 Fe(III) or Cu(II) ions in NMP were investigated and the main observed reactions were EB-PANI oxidation to pernigraniline (PB-PANI) and EB-PANI doping process by pseudo-protonation, or by a two-step redox process. In the presence of O 2, PB-PANI is observed in all Fe(III)/EB solutions and EB-PANI doping only occurs in solutions with high Fe(III) concentrations through pseudo-protonation. On the other hand, emeraldine salt (ES-PANI) is formed in all Fe(III)/EB solutions under N 2 atmosphere and, in this case, doping occurs both by the pseudo-protonation and two-step redox mechanisms. In all Cu(II)/EB solutions PB-PANI is formed both in the presence and absence of O 2, and only for solutions with high Cu(II) concentrations doping process occurs in a very low degree. The most important result from EPR spectra was providing evidence for redox steps. The determined Cu(II) signal areas under oxygen are higher than under N 2 and, further, the initial metal proportions (1:2:20) are maintained in these spectra, indicating that Cu(I) formed are re-oxidized by O 2 and, so, Cu(II) ions are being recycled. Consistently, for the solutions prepared under nitrogen, the corresponding areas and proportions in the spectra are much lower, confirming that a partial reduction of Cu(II) ions actually occurs.

Spectroscopic investigation of the interactions between emeraldine base polyaniline and Eu(III) ions

The interactions of emeraldine base form of polyaniline (EB-PANI) and Eu(III) ions in 1-methyl-2-pyrrolidinone (NMP) solution and in films have been investigated by UV–vis–NIR, resonance Raman, luminescence and electron paramagnetic resonance (EPR) spectroscopies. These spectroscopic techniques allowed to characterize quinone and semiquinone segments in the polymeric chains, and the oxidation state of europium ions in Eu-PANI samples. For high values of Eu(III)/N molar ratio (24/1) the presence of a weak polaronic absorption band at 980 nm in UV–vis–NIR spectrum and the observation of bands at 1330 and 1378 (ν C–N +) cm −1 due to emeraldine salt in the Raman spectrum at 1064 nm indicate a low doping degree. Oxidation of EB-PANI to pernigraniline base (PB-PANI) occurs in diluted solutions. The experimental data showed that the solvent plays an important role on the nature of formed species. The narrow EPR signal at g = 2.006 (line width 8G) confirms the presence of PANI radical cations in Eu-PANI film. The absence of broad signal characteristic of Eu(II) in EPR spectrum suggested that europium ions are primarily at Eu(III) oxidation state. The luminescence spectra of Eu-PANI film presented emission bands at 405 and 418 nm assigned to PANI moieties and bands at 594, 615 and 701 nm assigned to 5D 0 → 7F J ( J = 1, 2 and 4, respectively) transitions of Eu(III). EPR and photoluminescence data confirm that europium ions are mainly in Eu(III) oxidation state in Eu(III)/PANI films.

Thermal and dc Conductivity Behavior of Fly Ash Filled Polyaniline Composites

In this paper temperature dependence of dc conductivity (σdc) of emeraldine base form of polyaniline (PANI) and fly ash filled PANI are presented. Samples were prepared by in situ polymerization of aniline using ammonium persulphate as an oxidant and hydrochloric acid as dopant. Fly ash filled PANI composites were prepared by adding 3 gms of fly ash. Thermal characteristics of samples were measured using differential scanning calorimetry. The dc conductivity (σdc) of fly ash filled PANI was found to be on the order of 1.63 × 10−11 s/cm at room temperature, which was lower than that of pure PANI. The activation energies calculated from σdc for PANI and the PANI 3 fly ash system were 1.35 and 1.16 eV, respectively. It was found that addition of fly ash to PANI drastically decreased the enthalpy from 2259.2 to 196.6 mJ. the endothermic peak due to the glass transition temperature shifted from 99.8 to 94.6°C. This was attributed to the change in the morphology of the composites on adding fly ash, as observed in the scanning electron micrographs.