Carbonized polyaniline cryogel: A spectroscopic study

Cryogels are chemically or physically crosslinked systems of polymer chains swollen with water. They are produced by the preparation of conducting polymers in frozen media, in ice. They contain a conducting component, typically a conducting polymer, such as polyaniline [1] and suitable supporting polymer. Raman spectroscopy allows for the analysis of wet samples or of aqueous solutions. Freeze-dried polyaniline cryogel has been prepared from polyaniline and was also analyzed with Raman spectroscopy. The carbonization has been followed by thermogravimetric analysis in inert atmosphere [2]. The macroporous morphology of polymer aerogel was retained after carbonization (Fig. 1). Raman spectra of polyaniline salt at 20 and 100 oC present the bands of the phenazine-like segments in polyaniline at 1646, 1401 and 578 cm–1, indicating extensive cross-linking of units (Fig. 2) [3]. The conversion to nitrogen-containing carbon is complete at 500 °C. Please click Additional Files below to see the full abstract

Polyaniline cryogels: Soft and conducting

Polyaniline is important conducting polymer [1]. It is prepared by the oxidation of aniline with ammonium peroxydisulfate in acidic aqueous media [2] (Fig. 1). When the oxidative polymerization of aniline is carried out in the presence of a water-soluble supporting polymer in frozen reaction media, in ice, a composite hydrogels are obtained after thawing. Such hydrogels are called cryogels and the prefix cryo refers to the way of their preparation. Please click Additional Files below to see the full abstract

Carbonized leather waste with deposited polypyrrole nanotubes: Conductivity and dye adsorption

This paper reports the conversion of a waste to a conducting material, exploiting the ability to adsorb pollutant organic dyes. Leather waste was carbonized at 800 °C in an inert nitrogen atmosphere. The resulting biochar was used for in-situ deposition of polypyrrole nanotubes produced by the oxidative polymerization of pyrrole in the presence of methyl orange. The composites of carbonized leather with deposited polypyrrole nanotubes of various composition were compared with similar composites based on globular polypyrrole. Their molecular structure was characterized by infrared and Raman spectra. Both conducting components formed a bicontinuous structure. The resistivity was newly determined by a four-point van der Pauw method and monitored as a function of pressure applied up to 10 MPa. The typical conductivity of composites was of the order of 0.1 to 1 S cm−1 and it was always higher for polypyrrole nanotubes than for globular polypyrrole. The method also allows for the assessment of mechanical features, such as powder fluffiness. The conductivity decreased by 1–2 orders of magnitude after treatment with ammonia but still maintained a level acceptable for applications operating under non-acidic conditions. The composites were tested for dye adsorption, specifically cationic methylene blue and anionic methyl orange, using UV-vis spectroscopy. The composites were designed for future use as functional adsorbents controlled by the electrical potential or organic electrode materials.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (RP/CPS/2022/005)Ministry of Education, Youth and Sports of the Czech Republic [RP/CPS/2022/005

Cotton fabric coated with conducting polymers and its application in monitoring of carnivorous plant response

The paper describes the electrical plant response to mechanical stimulation monitored with the help of conducting polymers deposited on cotton fabric. Cotton fabric was coated with conducting polymers, polyaniline or polypyrrole, in situ during the oxidation of respective monomers in aqueous medium. Thus, modified fabrics were again coated with polypyrrole or polyaniline, respectively, in order to investigate any synergetic effect between both polymers with respect to conductivity and its stability during repeated dry cleaning. The coating was confirmed by infrared spectroscopy. The resulting fabrics have been used as electrodes to collect the electrical response to the stimulation of a Venus flytrap plant. This is a paradigm of the use of conducting polymers in monitoring of plant neurobiology.Web of Science164art. no. 49

One-dimensional nanostructures of polypyrrole for shielding of electromagnetic interference in the microwave region

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−1), 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% w/w). Resulting lightweight and flexible polypyrrole composites exhibit promising properties for shielding of electromagnetic interference in sensitive biological and electronic systems. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech Republicproject DKRVO [RP/CPS/2020/006]; [A2_FCHI_2020_030

Coating of leather with dye-containing antibacterial and conducting polypyrrole

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic dyes: crystal violet, neutral red, methyl orange, acriflavine, and methylene blue. This technique ensures the uniform coating of collagen fibers with polypyrrole and incorporation of organic dyes. The surface morphology was observed with scanning electron microscopy and the transverse profile, reflecting the penetration of the conducting phase into the leather body with optical microscopy. While the polypyrrole coating endows leather with electrical conductivity, organic dyes are expected to affect the polymer morphology and to provide an antibacterial effect. The lowest sheet resistance and antibacterial activity were obtained with crystal violet. This type of coating was characterized in more detail. Infrared spectroscopy confirmed the coating of collagen fibers with polypyrrole and dye incorporation. Mechanical properties were extended to the cyclic bending of the leather at various angles over 5000 cycles. The relative resistance changes were a few percent, indicating good electrical stability during repeated mechanical stress.Ministry of Education, Youth and Sports of the Czech Republic [FRC RO70200003025/2102]Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: FRC RO70200003025/210

Bidisperse magnetorheological fluids utilizing composite polypyrrole nanotubes/magnetite nanoparticles and carbonyl iron microspheres

Conductive polypyrrole nanotubes were synthesized with a two-step one-pot synthesis. During synthesis, the nanotubes were decorated with magnetite nanoparticles at different concentrations granting them magnetic properties. The characterization of the tubes revealed differences from the theoretical reactions. A bidisperse magnetorheological fluid (MRF) was prepared by mixing the composite polypyrrole nanotubes/magnetite nanoparticles with commercial carbonyl iron spherical microparticles in silicone oil. The rheological properties of the bidisperse system were studied under the presence of magnetic field at room and elevated temperature. An enhancement of the MR effect with the presence of the nanotubes was observed when compared with a standard MRF consisted only of magnetic microparticles. Due to the faster magnetic saturation of the nanotubes, this enhancement is exceptionally high at low magnetic fields. The stability of the system is studied under dynamic conditions where it is revealed that the nanotubes keep the standard particles well dispersed with the sedimentation improving by more than 50%.Internal Grant Agency of Tomas Bata University in Zlín, (IGA/CPS/2022/004, RP/CPS/2022/003); National Technical Library in Prague; Tomas Bata University in Zlin, TBU; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, MŠMT; en:MEYS, (RP/CPS/2022/007); Univerzita Tomáše Bati ve ZlíněNational Technical Library in Prague; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2022/004]; project DKRVO [RP/CPS/2022/007, RP/CPS/2022/003]; Ministry of Education, Youth and Sports of the Czech Republi

Pressure-sensitive conducting and antibacterial materials obtained by in situ dispersion coating of macroporous melamine sponges with polypyrrole

Melamine sponges were coated with polypyrrole during the in situ polymerization of pyrrole. The precipitation polymerization was compared with the dispersion mode, that is, with the preparation in the presence of poly(N-vinylpyrrolidone) and nanosilica as colloidal stabilizers. The coating of sponges during the dispersion polymerization leads to the elimination of the undesired polypyrrole precipitate, improved conductivity, and increased specific surface area. The sponges were tested with respect to their conductivity and as pressure-sensitive conducting materials with antibacterial performance. © 2021 The Authors. Published by American Chemical Society.Czech Science FoundationGrant Agency of the Czech Republic [19-04859S, 21-09830S]; internal Prague University research project [A2_FCHI_2021_003]; Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [DKRVO RP/CPS/2020/001]RP/CPS/2020/001; A2_FCHI_2021_003; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Grantová Agentura České Republiky, GA ČR: 19-04859S, 21-09830

Conducting and magnetic hybrid polypyrrole/nickel composites and their application in magnetorheology

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.Grantová Agentura České Republiky, GA ČR, (22-25734S, 23-07244S)Czech Science Foundatio

Polypyrrole nanotubes and their carbonized analogs: Synthesis, characterization, gas sensing properties

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 n-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. © 2016 by the authors; licensee MDPI, Basel, Switzerland