Preparation,FTIR spectroscopic characterization and isothermal stability of differently doped conductive fibers based on polyaniline and polyacrylonitrile

Conductive fibers based on polyaniline (PANI) and polyacrylonitrile (PAN) were obtained by stirring with magnetic bar. This research was conducted to investigate conducting fibers of polyaniline:polyacrylonitrile (PANI:PAN) composite with different weight ratios of aniline in PAN matrix. The fibers were prepared by stirring process. The best conductivity behavior of the fibers was obtained with 5 mL of aniline. The fibers obtained were characterized using Fourier-transform infrared spectra (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The variation of electrical conductivity with different type doping agents (HCl, H₂SO₄ and HClO₄) and the stability in terms of DC electrical conductivity retention was studied in an oxidative environment by isothermal characteristics.     

Electrical behavior of conducting polymer based ‘polymeric–inorganic’ nanocomposite: Polyaniline and polypyrrole zirconium titanium phosphate

Composites are 21st century material used to meet the demand of improved materials and possess a combination of several desirable properties. Present study focussed on the conducting behavior of ‘polymeric–inorganic’ nanocomposite of conducting polymer polyaniline and polypyrrole. ‘Polymeric–inorganic’ nanocomposite cation-exchangers, i.e., polyaniline zirconium titanium phosphate (PANI-ZTP) and polypyrrole zirconium titanium phosphate (PPy-ZTP), were synthesized via sol–gel mixing of electrical conducting polymers into the matrices of inorganic precipitate of zirconium titanium phosphate (ZTP) having excellent ion exchange properties. The proposed nanocomposite possessed DC electrical conductivity in the semi-conducting range, i.e., 10^?5–10^?3 S cm^?1. The stability in terms of DC electrical conductivity retention was also studied in an oxidative environment by two slightly different techniques viz. isothermal and cyclic techniques. The DC electrical conductivity of composite material was found stable upto 110 °C under ambient conditions.     

Morphology and electrical properties of hybrid and sulphonated oxalic acid-doped polyaniline

Polyaniline–polyethylene glycol2000 (PAni–PEG2000) hybrid and sulphonated polyaniline (SPAni) were prepared using oxalic acid as dopant and potassium permanganate as oxidant. The properties of these two conductive polymers were studied in comparison with pure polyaniline (PAni) prepared using the same conditions. The investigated polymers were characterized using FTIR, UV–vis, TGA, TEM, SEM, XRD and their electrical conductivities were also investigated. The morphology of pure polymer was found to be flat ribbon-like form, while presence of polyethylene glycol led to the formation of separate nanospheres. The three polymer samples have different degrees of crystallinity, the highest degree is for SPAni. Unexpectedly, electrical conductivity is in the order SPAni > PAni–PEG2000 > PAni, aging of PAni increases gradually the conductivity of the polymer from 0.0056 to 0.023 S cm^?1 and the increase of temperature gradually decreases the conductivity.     

High thermoelectric performance of poly(2,5-dimethoxyphenylenevinylene) and its derivatives

Poly(2,5-dimethoxyphenylenevinylene) (PMeOPV) and a series of copolymers consisting of both 2,5-dimethoxy-substituted phenylenevinylene units and unsubstituted units (P(MeOPV-co-PV)) were evaluated from the viewpoint of their thermoelectric properties. Their conjugated polymer films were prepared by pyrolysis of stretched or unstretched films of sulfonium salt precursor polymers, and subsequently doped with iodine vapor to provide electrical conductivity. The power factors P (=S²σ), indicating thermoelectric performance, were calculated with the measured electrical conductivity σ and Seebeck coefficient S of the doped films. PMeOPV showed a higher power factor of 7.1 μW m⁻¹ K⁻² at 313 K than that of a camphorsulfonic acid-doped polyaniline as reference. P(MeOPV-co-PV) precursor polymers with less than 20 mol% of MeOPV unit content in the monomer feed were stretchable, therefore providing stretched P(MeOPV-co-PV) films with low MeOPV unit content. The stretching treatment for P(MeOPV-co-PV) enhanced its electrical conductivity, but kept the Seebeck coefficient at nearly the same level as that of unstretched polymers. Consequently a 4.4-fold stretched copolymer exhibited an electrical conductivity of 183.5 S/cm and a Seebeck coefficient of 43.5 μV/K at 313 K, and thus, its power factor at 313 K was over 30 μW m⁻¹ K⁻². To the best of our knowledge, this is the highest thermoelectric performance ever reported among conducting polymers.     

Effect of pressure on the morphology of polyaniline nanostructures

We present experimental results regarding the effects of applied pressure on the morphology and electrical conductivity of polyaniline/HClO₄ nanostructures synthesized via dilute polymerization. By applying a local pressure of 4000 psi (28 MPa) to the nanostructured network, the morphology of the network was transformed to that of a continuous film. The conductivity shows a concomitant increase for the temperature range of 250–300 K. We assign this enhancement of room temperature conductivity to an increase in the effective contact areas between the previously fibrous structures leading to a shorter charge transport path length as the morphology of the film is transformed from a nanostructured network to a continuous film.     

Magnetic behavior of polyaniline doped with oxidized ferrocenesulfonic acid

Ferrocenesulfonic acid (FSA) was oxidized by iodine (I₂) and then used as dopant for polyaniline emeraldine base. The resulted polyaniline showed an electrical conductivity of 4.50 × 10⁻² S/cm and a ferromagnetic interaction with a positive Weiss constant of 15 K, the magnetic behavior is attributed to the ferromagnetic coupling between ferrocenium cations in the counter-ions along the polyaniline chain.     

Optical and electrical characterizations of ZnS nanoparticles embedded in conducting polymer

ZnS nanoparticles of average size (5 nm) have been prepared using thioglycerol. Inorganic–organic hybrid nanocomposites have been synthesized by dispersing nanosized ZnS in the conducting polyaniline matrix. The samples have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM) and UV–vis spectrophotometer. The wavelength of optical absorption peak of ZnS nanoparticle increases from 270 to 330 nm with the decrease of polyaniline concentration. Studies on direct current (DC) electrical conductivity as a function of temperature suggest that three-dimensional Mott’s hopping process occurs in ZnS–polyaniline nanocomposites. The correlated barrier hopping is confirmed from temperature dependent alternating current (AC) conductivity. The incorporation of ZnS nanoparticles enhances the barrier height.     

Preparation and electrical–magnetic properties of polyaniline doped with ionic ferrocenesulfonic acid

Conducting polyaniline with electrical conductivity of 2.34 × 10⁻¹ S cm⁻¹ was obtained using ferrocenesulfonic acid as dopant. After the ferrocenesulfonic acid was oxidized with FeCl₃, though the electrical conductivity of the doped polyaniline decreased by 1–2 orders of magnitude, the magnetic susceptibility (χ) increased with the increase of the oxidation degree of ferrocenesulfonic acid. EPR spectra showed not only a signal with a g value of around 2, but also a so-called half-field signal with a g value of about 4 even at room temperature. Coexistence of ferromagnetic intrachain interactions and antiferromagnetic interchain interactions in the materials has been suggested.     

Thermoelectric figure-of-merit of iodine-doped copolymer of phenylenevinylene with dialkoxyphenylenevinylene

The copolymers consisting of both unsubstituted and 2,5-dialkoxy-substituted phenylenevinylenes (P(ROPV-co-PV); RO = MeO, EtO and BuO) with ca. 30 mol% of dialkoxy-substituted units were synthesized to evaluate their thermoelectric properties. Iodine-doped P(ROPV-co-PV) exhibited high Seebeck coefficient with relatively high electrical conductivity among electrically conductive polymers ever reported. The effect of the stretching treatment on their thermoelectric properties was examined. Consequently, both P(MeOPV-co-PV) and P(EtOPV-co-PV) constantly showed high Seebeck coefficients with increased electrical conductivities by the stretching alignment because of an increase in the carrier mobility, while the Seebeck coefficient of P(BuOPV-co-PV) varied inversely with a variation of the electrical conductivity. We also evaluated thermal conductivity of the pristine and iodine-doped P(ROPV-co-PV) for calculations of their thermoelectric figure-of-merit ZT. To the best of our knowledge, consequent thermoelectric figure-of-merit ZT of all the iodine-doped copolymer with the stretch treatment is one of the highest thermoelectric performance among conducting polymers reported ever, which are comparable with that of an inorganic thermoelectric materials, such as β-FeSi₂.     

Polypyrrole and polyaniline prepared with cerium(IV) sulfate oxidant

The conducting polymers, polypyrrole and polyaniline, were synthesized by chemical oxidative polymerization of the corresponding monomers in 0.1 M sulfuric acid using cerium(IV) sulfate as the oxidant at mole ratios of oxidant-to-monomer ranging from 0.5 to 3. The yields of the oxidation products were determined, and the samples were characterized with respect to their elemental composition, molecular structure, and morphology. The conductivity of polypyrrole prepared in 0.1 M sulfuric acid, 10^?1 to 10⁰ S cm^?1, was higher compared with the conductivity of polyaniline prepared under the same conditions, 10^?3 to 10^?1 S cm^?1. The loss of mass after deprotonation with ammonium hydroxide is reported, and discussed in terms of the type of protonation as also reflected by FTIR spectroscopy. The conductivity of polypyrrole bases remained at relatively high level, 10^?5 to 10^?3 S cm^?1, while PANI bases became non-conducting, 10^?12 to 10^?10 S cm^?1. The polymers had a granular morphology in all cases.     

Electrical and magnetic properties of the Fe3O4–polyaniline nanocomposite pellets containing DBSA-doped polyaniline and HCl-doped polyaniline with Fe3O4 nanoparticles

DBSA-doped polyaniline (DBSA–PANI) powder and HCl-doped polyaniline with Fe₃O₄ nanoparticles (HCl–PANI–Fe₃O₄) powder were mechanically mixed to obtain the Fe₃O₄–polyaniline nanocomposites. Powders of the nanocomposites were pressed to the pellets. Micromorphology, electrical and magnetic properties of the nanocomposite pellets were studied by using scanning electron microscopy and by measuring the conductivity in 100–300 K and the magnetization curve at room temperature. The DBSA–PANI pellets consist of long fibrils while the HCl–PANI–Fe₃O₄ pellets consist of granular particles. Thus the Fe₃O₄–polyaniline nanocomposites pellets consist of long fibrils and granular particles. The conductivity of the nanocomposite pellets linearly decreases from 0.19 ± 0.06 to 0.05 ± 0.01 S/cm when the HCl–PANI–Fe₃O₄ content increases from 0 to 100 wt.%. The variation of conductivity with temperature reveals that the charge transport mechanism can be considered to be one-dimensional variable-range-hopping (1D-VRH). All the Fe₃O₄–polyaniline nanocomposites show the magnetization curves. The saturation magnetization monotonously increases with increasing HCl–PANI–Fe₃O₄ content while the coercivity is estimated to be about zero independent of the HCl–PANI–Fe₃O₄ content. The saturation magnetization of the HCl–PANI–Fe₃O₄ is 11 emu/g.     

Characterization of water-soluble externally HCl-doped conducting polyaniline

Water solubility in all pH region for externally HCl-doped conducting polyaniline (ED-SPAN) enables us to do its detail characterization by UV–VIS spectra, cyclic voltammogram, ESR spectra, and electrical conductivity in relation to the doping level. It was found that one free radical was produced in polyaniline backbone by the addition of one proton onto the imino-nitrogen. The electrical conductivity of ED-SPAN solid film remarkably increased with increasing free radical in polyaniline backbone because of remarkable increase of the hole mobility. Undoping of ED-SPAN solid occurred by heating at more than 40 °C.     

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.     

Highly conducting electrospun polyaniline-polyethylene oxide nanofibrous membranes filled with single-walled carbon nanotubes

Highly conducting nanofibrous composite of well-oriented single-walled carbon nanotubes (SWNTs) in polyaniline (PANI) and polyethylene oxide (PEO) have been fabricated using electrospinning. The room temperature electrical conductivity show nearly four order enhancement with highest (11.9 wt%) loading of SWNT in the PANI–PEO blend. The temperature dependent conductivities are measured in the range of 30–300 K and the results are analyzed by the fluctuation assisted tunneling model.     

Conducting polymer embedded with nanoferrite and titanium dioxide nanoparticles for microwave absorption

The present paper deals with the synthesis of conducting ferrimagnetic polyaniline nanocomposite embedded with γ-Fe₂O₃ (9–12 nm) and titanium dioxide (70–90 nm) nanoparticles via a micro-emulsion polymerization. The microwave absorption properties of nanocomposite in 12.4–18 GHz (Ku-band) frequency range shows shielding effectiveness due to absorption (SE_A) value of ?45 dB, which is much higher than polyaniline composite with iron oxide and polyaniline–TiO₂ composites. The higher EMI shielding is mainly arising due to combined effect of γ-Fe₂O₃ and TiO₂ that leads to more dielectric and magnetic losses which consequently contributed to higher values of shielding effectiveness. XRD analysis of the nanocomposite reveals the incorporation of nanoparticles in the conducting polymer matrix while the thermal gravimetric analysis (TGA) demonstrates that the nanocomposite is stable up to 250 °C.     

Preparation of polyaniline–TiO2 composite and its comparative corrosion protection performance with polyaniline

Due to strict environmental regulations on the usage of chromate in the coating industries, search for effective inhibitive pigment in replacing those chromate pigments has become necessary. In recent years it has been shown that electrically conducting polymers such as polyaniline (PANI) incorporated coatings are able to protect steel due to their passivating ability similar to that of chromates. This work presents the comparative corrosion protection performance of the coatings containing polyaniline and polyaniline–TiO₂ composite (PTC) on steel in acrylic binder. The PANI and PTC were prepared by chemical oxidative method of aniline by ammonium persulfate. The polymers were characterized by FTIR, XRD and SEM. The corrosion protection performance of the coatings containing PANI and PTC on steel was evaluated by immersion test in 3% NaCl for 60 days and salt fog test for 35 days. The performance of the coatings in both the tests was investigated by open circuit potential measurements and EIS technique. It has been found that the open circuit potential values of PTC containing coating are more nobler by 50–200 mV in comparison to that of coatings with PANI. Besides, the resistance values of the coating containing PTC were more than 10⁷ Ω cm² in the 3% NaCl immersion test after 60 days and 10⁹ Ω cm² in the salt fog test of 35 days which were two orders high in comparison to that of PANI containing coatings. The better performance of PTC containing coatings may be due to uniform distribution of polyaniline which can form uniform passive film on the iron surface.     

MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers chemiresistor and their application in low molecular weight alcohol vapours sensing

Herein, we fabricated MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers by electrospinning and dip coating method. The amount of MWCNT–OH adsorbed to the pure electrospun nylon 6,6 nanofibers was 0.056 wt%. The electrical conductivity of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers was 5.24 × 10^?3 S cm^?1. We also investigated the sensing properties of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers by measuring its response upon exposure to low molecular weight alcohol vapours such as methanol, ethanol, 1-propanol, and 1-butanol. The changes of the electrical resistance of MWCNT–OH adsorbed electrospun nylon 6,6 nanofibers were demonstrated on the basis of hydrogen bonds among the alcohol vapours and hydroxyl groups (–OH) on MWCNT–OH, and amide groups (–NHCO–) in nylon 6,6. The fabricated sensor showed good reversible and reproducible responses upon the cyclic test.     

Polyurethane latex modified with polyaniline

The strategy of the modification of polyurethane latex with a conducting polymer, polyaniline, is proposed. It is based on the introduction of the polymer steric stabilizer to the latex. The stabilizer prevents the macroscopic precipitation of a conducting polymer during the polymerization. Polyaniline has been prepared by the oxidative polymerization of aniline in the presence of polyurethane latex with average particle size of 36 nm and poly(N-vinylpyrrolidone). Thus, modified latex produces an aqueous colloidal dispersion having the particle size 100–200 nm. The presence of poly(N-vinylpyrrolidone) was needed to obtain a colloid. In its absence, a polyaniline–polyurethane composite precipitated. The composite coatings obtained after their drying contained 5–18 wt.% polyaniline in a protonated emeraldine form, had the conductivity up to 10⁻² S cm⁻¹, and mechanical properties typical of elastomers.     

Novel properties of polyaniline nanofibers coated with polycatechol

Polyaniline nanofibers coated with polycatechol, FcPAn/polycatechol, have been prepared with two steps by using repeated potential cycling. First, aniline in a solution containing ferrocenesulfonic acid (Fc) was polymerized on a platinum electrode to form polyaniline nanofibers (FcPAn); second, catechol was polymerized on the polyaniline nanofibers to form FcPAn/polycatechol. The scanning electron microscopy (SEM) images show that the diameters of FcPAn and FcPAn/polycatechol fibers are in the range of 40–60 and 70–90 nm, respectively. The IR and XPS spectra of FcPAn/polycatechol indicate that OH groups and ferrocenesulfonic acid are contained in FcPAn/polycatechol. FcPAn/polycatechol has a good electrochemical activity in the wide pH range. The cyclic voltammogram identifies that FcPAn/polycatechol in the Na₂SO₄ solution with pH 11.0 still has the electrochemical activity at the scan rate of 60 mV s⁻¹. The conductivity of FcPAn/polycatechol is 0.48 S cm⁻¹, which is slightly affected by water. FcPAn/polycatechol nanofibers with the diameter of 70–90 nm have a higher catalytic activity to the electrochemical oxidation of ascorbic acid, compared with FcPAn/polycatechol fibers with the diameter of 140–210 nm.     

Nanostructured polyaniline synthesized using interface polymerization and its redox activity in a wide pH range

Purely nanostructured polyaniline with the conductivity of 7.2 S cm^?1 was synthesized via the quick addition of the oxidant of the solid ammonium peroxydisulfate into a cooled solution containing aniline and hydrochloric acid without any templates. The morphology of polyaniline is constructed of interwoven fibers with an average diameter of about 50 nm with lengths varying from 250 nm to 370 nm. In general, the conventional polyaniline completely lost its electric activity including conductivity and redox activity at pH 6; however, the polyaniline reported here shows two pairs of redox peaks on its cyclic voltammogram in 1.0 M NaCl solution with pH 7.0, which is similar to that of the conventional polyaniline in the more acidic solutions; and it still holds the redox activity until pH 9.0. The pH dependence of conductivity of polyaniline is also improved compared to that of the conventional polyaniline. The ESR measurements show that the deprotonated polyaniline still holds rather high unpaired spin densities. The ¹H NMR spectra of polyaniline synthesized using interface polymerization are different those of the conventional polyaniline. The electrochemical behavior and spectra of polyaniline synthesized via the quick addition of an oxidant solution into a solution of aniline were reported and discussed.