The present contribution reports the single-step preparation of new type of soft macroporous conducting cryogels, a special type of hydrogels. Polyaniline/poly(vinyl alcohol) cryogel was prepared by ...the oxidation of aniline hydrochloride in frozen reaction mixtures, in ice, containing a supporting polymer, poly(vinyl alcohol). The cryogel used for illustration contained of polyaniline, poly(vinyl alcohol) and 93 wt % of aqueous phase. It was macroscopically homogeneous and it had macroporous structure with average pore size of ≈100 μm. The conducting polyaniline phase was fibrillary. The molecular structure of polyaniline was confirmed by Raman spectroscopy. The conductivity of cryogel was 0.004 S cm–1 in water and 0.105 S cm–1 in 0.1 M sulfuric acid. It still increased to 0.29 S cm–1 when the content of monomer increased five times. Because of the contribution of electronic transport, the conductivity of cryogel was always higher than the ionic conductivity of aqueous phase used for its penetration. The conductivity of freeze-dried cryogel was 0.003 S cm–1. Viscoelastic and mechanical properties, controlled mainly by the conducting polymer phase, have been assessed and demonstrated good mechanical integrity and feasibility of potential applications.
Aniline and pyrrole have been oxidized with ammonium peroxydisulfate in aqueous solutions, in the presence of equimolar quantities of hydrochloric acid. The oxidation of pyrrole was faster; the ...induction period typical of aniline oxidation was absent in the case of pyrrole. As the proportion of oxidant-to-monomer molar concentration increased up to 1.5, the yield increased in both cases. Similarities between the two oxidations are illustrated and discussed. The oxidant-to-monomer molar ratio 1.25 is proposed to be the optimum stoichiometry, in the accordance with the data published in the literature. The conductivities of the polymers prepared were only slightly dependent on the oxidant-to-monomer ratio in the range 0.3–1.5, and were of the order of 10
0
S
cm
−1 for polyaniline and ∼10
−2–10
−1
S
cm
−1 for polypyrrole. Outside this interval, the conductivity of both polymers was reduced. Polyaniline having conductivity ∼10
S
cm
−1 was produced in solutions of phosphoric acid of various concentrations. On the contrary, the conductivity of polypyrrole was reduced as the concentration of phosphoric acid became higher. The type of protonation is discussed with the help of FTIR spectra by analyzing the ammonium salts obtained after deprotonation. Sulfate or hydrogen sulfate anions produced from peroxydisulfate always constitute a part of the counter-ions.
Polypyrrole one-dimensional nanostructures (nanotubes, nanobelts and nanofibers) were prepared using three various dyes (Methyl Orange, Methylene Blue and Eriochrome Black T). Their high electrical ...conductivity (from 17.1 to 60.9 S cm
), good thermal stability (in the range from 25 to 150 °C) and resistivity against ageing (half-time of electrical conductivity around 80 days and better) were used in preparation of lightweight and flexible composites with silicone for electromagnetic interference shielding in the C-band region (5.85-8.2 GHz). The nanostructures' morphology and chemical structure were characterized by scanning electron microscopy, Brunauer-Emmett-Teller specific surface measurement and attenuated total reflection Fourier-transform infrared spectroscopy. DC electrical conductivity was measured using the Van der Pauw method. Complex permittivity and AC electrical conductivity of respective silicone composites were calculated from the measured scattering parameters. The relationships between structure, electrical properties and shielding efficiency were studied. It was found that 2 mm-thick silicone composites of polypyrrole nanotubes and nanobelts shield almost 80% of incident radiation in the C-band at very low loading of conductive filler in the silicone (5%
). Resulting lightweight and flexible polypyrrole composites exhibit promising properties for shielding of electromagnetic interference in sensitive biological and electronic systems.
Polypyrrole nanotubes exhibit conductivity of tens S cm
−1
which is one of the highest among the current conducting polymers. They are thus superior to the common globular form with the conductivity ...of units of S cm
−1
or lower. The conductivity of both forms is reduced after treatment with alkalis but still remains high, units of S cm
−1
and 10
−2
S cm
−1
, respectively. The deprotonation, which is responsible for conductivity reduction, is discussed on the basis of salt-base transition in polypyrrole. It is not fully reversible, and the reprotonation with acids recovers the conductivity only in part. The role of methyl orange, which was used to support the formation of nanotubes, is proposed to be similar to that of surfactants. FTIR and Raman spectroscopies prove that methyl orange is strongly bound to polypyrrole in its acid form, and an "insertion" mechanism is proposed to explain the resistance towards the deprotonation of nanotubes. The spectra also illustrate that the molecular structure of nanotubular polypyrrole is preserved even under highly alkaline conditions at a pH close to 14, where the globular form becomes damaged. Polypyrrole, especially in its nanotubular form, is of promise in applications requiring electrical conduction even under neutral or alkaline conditions, where other conducting polymers, such as polyaniline, lose their exploitable conductivity.
Polypyrrole nanotubes exhibit conductivity of tens S cm
−1
which is one of the highest among the current conducting polymers.
The reaction between two nonconducting compounds, aniline and silver nitrate, yields a composite of two conducting products, PANI and silver. While the oxidation of aniline with silver nitrate is ...slow and takes over several months, the addition of a small amount of p-phenylenediamine, 1 mol % relative to aniline, shortens the reaction time to a few hours and, with higher concentrations of p-phenylenediamine, even to tens of minutes. Nonconducting aniline oligomers, however, are also present in the oxidation products as a rule. The chemistry of individual oxidation pathways is discussed. Higher concentrations of p-phenylenediamine in the reaction mixture with aniline give rise to copolymers, polyaniline-co-(p-phenylenediamine)s, and their composites with metallic silver. p-Phenylenediamine alone can similarly be oxidized with silver nitrate to poly(p-phenylenediamine) composite with silver. Silver is present in the composites both as nanoparticles of ∼50 nm size and as larger objects. The composites have conductivity in the range of the order of 10−3−103 S cm−1 at comparable content of silver, which was close to the theoretical expectation, 68.9 wt %. The composites prepared in 1 M acetic acid always have a higher conductivity compared with those resulting from synthesis in 1 M nitric acid. The polymerizations of aniline accelerated with 1 mol % of p-phenylenediamine in 1 M acetic acid yield a composite of the highest conductivity, 6100 S cm−1. At higher contents of p-phenylenediamine, polyaniline-co-(p-phenylenediamine) composites with silver have a conductivity lower by several orders of magnitude. The oxidation of p-phenylenediamine alone with silver nitrate in 1 M acetic acid also yields a conducting composite, its conductivity being 1750 S cm−1. The semiconductor type of conductivity in polymers and the metallic type of conductivity in silver may compensate to yield composites with conductivity nearly independent of temperature over a broad temperature range.
•Development of flexible nanocellulose-based carbon black@polyaniline electrodes.•Enhancement of the specific capacity and cycling stability by nanostructuring of PANI.•Green and cost-effective way ...to prepare high-performance pseudocapacitive electrode.
Flexible, lightweight and electrically conductive composites based on renewable resources have recently attracted a growing interest for the development of high performance sustainable energy storage devices that can meet the needs of modern wearable and portable electronics. Herein, we developed a high performance carbon black@polyaniline (PANI) based flexible electrodes using a facile, low cost and environmentally friendly strategy. The strategy consisted of a co-deposition and nanostructuring of PANI layer with tailored morphology on the surface of carbon black and nanofibrillated cellulose (NFC) via in situ polymerization. NFC acted as a mechanical skeleton and imparted the electrode with strength and flexibility to ensure excellent electrochemical performance. The co-doping of PANI chains via a combination of a primary/secondary dopant, namely, HCl/poly(2-acrylamido-2-methyl-1-propanesulfonic acid), was used to control the morphology of PANI. Correlation between the textural properties of the carbon black, NFC loading, and the properties of the resulting electrodes was established. The maximum specific capacitance of 363±9 F/g at the potential scan rate of 50 mV/s was exhibited by the electrode with 60% of active material loading, for which an effective growth of hierarchical nanostructures of carbon black@PANI on the surface of NFC was achieved, leading to the highest specific surface area of the composite (861 m2/g) and a to a microporosity/mesoporosity balance. The remarkable cycling stability of the hybrid electrodes was attained as the specific capacitance retention was close to 100% with a negligible capacity decay within the tested period (over 500 cycles) regardless of the amount of the active material. This study provides an eco-friendly and cost-effective way to prepare high performance flexible electrodes for pseudo-capacitors
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Hybrid organic/inorganic conducting and magnetic composites of core-shell type have been prepared by in-situ coating of nickel microparticles with polypyrrole. Three series of syntheses have been ...made. In the first, pyrrole was oxidised with ammonium peroxydisulfate in water in the presence of various amounts of nickel and the composites contained up to 83 wt% of this metal. The second series used 0.1 M sulfuric acid as a reaction medium. Finally, the composites with polypyrrole nanotubes were prepared in water in the presence of structure-guiding methyl orange dye. The nanotubes have always been accompanied by the globular morphology. FTIR and Raman spectroscopies confirmed the formation of polypyrrole. The resistivity of composite powders of the order of tens to hundreds Ω cm was monitored as a function of pressure up to 10 MPa. The resistivity of composites slightly increased with increasing content of nickel. This apparent paradox is explained by the coating of nickel particles with polypyrrole, which prevents their contact and subsequent generation of metallic conducting pathways. Electrical properties were practically independent of the way of composite preparation or nickel content and were controlled by the polypyrrole phase. On the contrary, magnetic properties were determined exclusively by nickel content. The composites were used as a solid phase to prepare a magnetorheological fluid. The test showed better performance when compared with a different nickel system reported earlier.
Four different leathers and a nonwoven fibrous mat have been coated with a conducting polymer, polyaniline, in situ during the oxidation of aniline hydrochloride in the presence of ...poly(N-vinylpyrrolidone) stabilizer. This colloidal dispersion approach prevented the undesirable formation of free polyaniline precipitate outside the leather fibers. The molecular structure of polypeptide fibers with deposited polyaniline is discussed on the basis of FTIR spectra. Raman spectroscopy confirmed that individual fibers were coated with a conducting polymer. The cross-sectional optical microscopy revealed that the leather was coated on both sides. The layer thickness, tens to hundreds micrometers, was determined by the penetration depth of reaction mixture. In the case of diabetic insole mat gambrela, polyaniline penetrated throughout the sample body. This was also confirmed by the measurement of transversal resistance. The typical sheet resistance was in units to hundreds kΩ/sq and differed but was of the same order of magnitude on top and bottom sides. The samples were subject to cyclic bending and of the resistivity changes have been monitored. Antibacterial activity of some leathers improved after the coating with polyaniline.
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•The samples of leather were coated with a conducting polymer.•Polyaniline was deposited in-situ using a colloidal dispersion mode.•Various modes of electrical resistance determination are provided.•A new method testing the resistance changes upon cyclic bending was developed.•The applications of conducting leather composites are proposed.
Polypyrrole (PPy) in globular form and as nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the absence and presence of methyl orange, respectively. They were ...subsequently converted to nitrogen-containing carbons at 650 °C in an inert atmosphere. The course of carbonization was followed by thermogravimetric analysis and the accompanying changes in molecular structure by Fourier Transform Infrared and Raman spectroscopies. Both the original and carbonized materials have been tested in sensing of polar and non-polar organic vapors. The resistivity of sensing element using globular PPy was too high and only nanotubular PPy could be used. The sensitivity of the PPy nanotubes to ethanol vapors was nearly on the same level as that of their carbonized analogs (i.e., ~18% and 24%, respectively). Surprisingly, there was a high sensitivity of PPy nanotubes to the
-heptane vapors (~110%), while that of their carbonized analog remained at ~20%. The recovery process was significantly faster for carbonized PPy nanotubes (in order of seconds) compared with 10 s of seconds for original nanotubes, respectively, due to higher specific surface area after carbonization.
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