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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 RO70200003025/2102

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, 21-09830S

The present feature article offers a concise overview of recent research progress of the authors working in the design of macroporous conducting materials represented by polypyrrole-coated melamine sponges. The article highlights innovative results from the authors and suggests a perspective for future directions in the field of macroporous conducting polymer composites. The article also overviews this particular subject area and defines key challenges for this emerging field. The feasibility of diverse applications of polypyrrole/melamine sponges is demonstrated and includes deformation-sensitive materials, electromagnetic radiation shielding and electrically heated insulation materials. Cytotoxicity is addressed with respect to applications in biomedicine, and the adsorption of an organic dye serves as an example of the uses in environmental water-pollution treatment. A single-step deposition of polypyrrole during the oxidative polymerization of pyrrole provides the uniform coating of the sponge with an organic conducting phase. The conductivity of sponges was of the order of 10−3 S cm−1, increased with polypyrrole loading, and also by two orders of magnitude after the compression. Derived materials have also been prepared and tested. They are represented by polypyrrole-coated sponge converted by pyrolysis to a macroporous nitrogen-containing carbon, magnetic ferrosponge obtained by incorporation of magnetite, or the conventional globular polypyrrole coating replaced with polypyrrole nanotubes. Polypyrrole can also be simply decorated with silver nanoparticles. The macroporous conducting polypyrrole/melamine sponges and derived materials are considered to be of future scientific interest with broad application potential.

Homovanillate (HVA) and vanilmandelate (VMA) are recognized markers of diseases, including neuroblastoma. However, their detection in urine represents a challenging task due to the complexity of the matrix. Here, a design, synthesis and thorough investigation of polymerizable urea-based receptors interacting with HVA and VMA are reported. The selection of receptor with the best anion recognition properties for electrode coating is based on

Polyaniline (PANI) salts with tungstosilicic (TSA) and phosphotungstic acids (PTA) were prepared by reprotonation of PANI base. Partial protonation of the precursor base was confirmed by Raman spectroscopy and by conductivity measurements. Conductivity of polyaniline tungstosilicate (PANI-TSA) and polyaniline phosphotungstate (PANI-PTA) after reprotonation measured on compressed pellets was found to be 1 × 10–5 S cm−1 and 4 × 10–6 S cm−1, that is significantly higher compared to conductivity of PANI base (⁓ 10–11 S cm–1). According to thermogravimetric and elemental analyses, the amount of heteropolyacids in the resulting salts was ≈ 20 wt%, which corresponded to ≈ 15 wt% of tungsten. Tungsten- and nitrogen-containing carbon derivatives were obtained by carbonization of the prepared PANI salts without losing their conductivity (⁓10–7 S cm–1). Successful carbonization was confirmed by vibrational spectroscopy. Electron microscopy showed that globular morphology typical for PANI base was not affected by reprotonation and carbonization procedures. Elemental analysis confirmed 25.6 and 17.9 wt% of tungsten, 9.7 and 9.6 wt% of nitrogen in the carbonized PANI-PTA and PANI-TSA, respectively. The prepared carbon derivatives can be potentially useful for electrocatalysis.

The study aims at the design of nanostructured hybrid materials that are both conducting and magnetic. Conducting polypyrrole nanotubes were prepared by the oxidation of pyrrole with iron(III) chlo...

The conductive polymer-electrolyte interface plays an important role in many electrochemical devices. An unusual situation arises when a solvent-free ionic liquid (SF-IL) is used as the electrolyte because it behaves as a molten salt rather than an electrolyte solution. On the basis of Raman spectra, it was found that the presence of ion pairs of SF-IL in the vicinity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) results in a decrease in the oxidation level of the polymer and an increase in the HOMO-LUMO gap. The process of polymer "dedoping" and the modification of the electronic structure of the polymer are illustrated by quantum chemical calculations.

Polypyrrole nanotubes were prepared by the oxidation of pyrrole in aqueous solutions of methyl orange and in the presence of 1–5 wt% of surface-active additives, surfactants, or amino acids. Three types of additives – anionic, non-ionic, and cationic – have been tested in the control of polypyrrole morphology and conductivity. The morphology of nanotubes was little dependent on surfactant type but the changes in size and aspect ratios were more pronounced with amino acids. Except for anionic surfactant, bis(2-ethylhexyl) sulfosuccinate, which behaved indifferently, all additives reduced the conductivity of polypyrrole, some even by four orders of magnitude. Based on FTIR spectroscopy, it is proposed that the hydrophobic interactions and/or hydrogen bonding between the additives and growing polypyrrole chains play the important role in reducing chain ordering, while the ionic interactions have limited effect.

Poly(aniline-co-m-phenylenediamine) cryogels supported by poly(vinyl alcohol) were obtained by oxidative cryocopolymerization of aniline and m-phenylenediamine in the presence of poly(vinyl alcohol) in the frozen aqueous medium. Morphology, specific surface area, and mechanical properties of aerogels obtained after freeze-drying with pore size up to 35 μm were dependent on initial freezing temperature and total concentration of comonomers in polymerization mixture. The materials initially frozen at higher temperatures and synthesized at higher comonomers concentrations were found to have in general smaller pore sizes and consequently better mechanical stability. Initial freezing temperature − 24 °C and total comonomer concentration 0.77 M were found to be the optimum parameters for the preparation of conducting cryogels with conductivity of solid phase 1 × 10−3 S cm−1, a relatively high specific surface area 23.1 m2 g−1, and excellent mechanical properties with tensile modulus 255 kPa. The molecular structure of cryogels is discussed with the help of FTIR and Raman spectra.

A facile preparation of a conducting one-dimensional polypyrrole nanostructure (1-D PPy) was achieved in the presence of safranin dye. The polymerization temperature has a significant effect on the conductivity, specific surface area and morphology of PPy. A decrease in the polymerization temperature leads to a significant increase in the conductivity. The highest conductivity was obtained by frozen polymerization (−24 °C) with a value of 175 ± 4 and 23.7 ± 2.9 S cm−1 for 1-D PPy and globular PPy, respectively. The temperature dependence of the conductivity of 1-D PPy prepared at −24 °C revealed a semiconducting behaviour with a 3-D variable range hopping charge transfer mechanism. Raman spectroscopy results suggested that the high conductivity can be attributed to the high protonation level of 1-D PPy. Nuclear magnetic resonance spectroscopy has been used to study the chemical structure of 1-D PPy and the incorporation of safranin into the polymer matrix.

A conducting polymer, polypyrrole, was deposited on tungsten disulfide flakes in situ during the oxidation of pyrrole. The conductivity of composites exceeded the conductivities of the parent components. This synergistic effect is explained by the deposition of more conducting ordered polypyrrole at first, and less conducting globular polypyrrole later after the whole available tungsten disulfide surface was coated. Such scenario was confirmed by electron microscopies. Raman and X-ray photoelectron spectroscopies proved the completeness of the coating. Despite the increase in the conductivity, the electrocatalysis of hydrogen evolution reaction on tungsten disulfide was reduced after polypyrrole deposition, confirming also effective coating of the substrate. A simple mixture of both components, however, improved the electrocatalytic effect compared with the composite or any of its components.

The microcomposites of a conducting polymer, polyaniline, with four layered zirconium phosphonates, viz. 4-sulfophenylphosphonate, 2-sulfoethylphosphonate, 4-carboxyphenylphosphonate, carboxymethylphosphonate, were prepared and characterized by wide-angle X-ray diffraction and FTIR and Raman spectroscopies. Aniline hydrochloride was proved to intercalate the hosts containing sulfonic group. The intercalation was not observed with the carboxyl-containing phosphonates. Two methods of aniline oxidation, using peroxydisulfate anion, cerium(IV) or iron(III) cations as aniline oxidants, were tested. FTIR and Raman spectra suggest that the intercalated aniline does not polymerize. Polyaniline grows on phosphonates during surface polymerization rather than to be generated as a free polymer in the bulk of reaction mixture. Conductivity varied from 10−9 S cm−1 to 10−3 S cm−1 depending on the way of preparation and the type of the phosphonate filler. The conductivity response to the ambient humidity strongly depends on the filler and suggests the possibility to apply these materials in humidity sensors.

Polypyrrole was prepared in the presence of cationic dyes, safranin and phenosafranin. The safranin supported the one-dimensional growth of polypyrrole, converting globules to nanorods and later also to nanotubes, particularly at higher dye concentrations. In the case of phenosafranin, the produced nanotubes were considerably thicker and were always accompanied by globules. Upon oxidation both dyes are expected to generate insoluble oligomeric templates that serve as loci for the deposition of polypyrrole. The formation of globular morphology takes place when the dye becomes depleted, due to its low concentration for safranin, or because of robust templates produced by phenosafranin. In addition to scanning and transmission electron microscopies, the resultant polypyrroles were characterized by FTIR and Raman spectroscopies, and DC conductivity measurements. The conversion of globular morphology to nanotubes/nanofibers was accompanied by the increase in conductivity from 5 to 35 S cm−1, which was explained by the improved ordering of polypyrrole chains more preferable for charge transport. The series of syntheses at varying oxidant-to-pyrrole mole ratios confirmed the stoichiometric ratio 2.5 to be the best for pyrrole oxidation but a good stability of polypyrrole was demonstrated even at extremely high stoichiometric ratio 15.

This study is focused on the visualization of latent fingerprints on brass surfaces using the method of electrochemical deposition of a polymer film based on poly(neutral red) (PNR). The experiment included (i) optimization of conditions of electrochemical deposition of PNR on brass surfaces, (ii) ATR-FTIR spectroscopic characterization of PNR-modified substrates, and (iii) identification of characteristic details on visualized fingerprints on fired brass cartridges. For electrochemical visualization, it is necessary to keep in mind both kind and “story” substrates. Experimental findings showed that electrochemical visualization carried out on brass plates is a step forward before known findings described in the literature and gives simultaneously a new approach for criminalists in the fight against crime.

New types of materials were produced by gradual heating of a conducting polymer, polypyrrole, to elevated temperatures. Three polymers differing in morphology - globules, nanofibers, and nanotubes - were exposed to temperatures from 100 to 700 degrees C in an argon atmosphere. The yields always exceeded 50 wt%, and the morphological features of the polymer were preserved. The transformation of polypyrrole salts to the corresponding bases followed by the carbonization was monitored by FTIR spectroscopy. The elemental analysis confirmed the subsequent conversion of polypyrrole to nitrogen-containing carbon. The specific surface areas were of the order of tens of m(2) g(-1); they increased from globules to nanotubes and nanofibers but were virtually independent of the exposition temperature. The conductivity of the powders was compared with that of the pellets when their preparation was possible. As the temperature was increased up to 400 degrees C, the conductivity decreased for all samples by ca. 5 orders of magnitude, e.g., for nanofibers from 10 to 10(-4) S cm(-1) but recovered to 10(-1) S cm(-1) after the subsequent carbonization up to 700 degrees C. Polypyrroles exposed to various temperatures were then tested for the adsorption of organic dye, Reactive Black 5, from water. The dye adsorption on original polypyrroles strongly depended on the polymer morphology. Polypyrrole nanofibers were able to remove the dye completely with a capacity of 100 mg g(-1), while the adsorption on polypyrrole globules was poor. The adsorption efficiency thus increased from globules to nanotubes and nanofibers. The adsorption performance was reduced after the carbonization, but the general trends were preserved. Postupným zahříváním vodivého polymeru polypyrrolu na zvýšené teploty byly vyráběny nové typy materiálů. Tři polymery lišící se morfologií - globule, nanovlákna a nanotrubice - byly vystaveny teplotám od 100 do 700 °C v argonové atmosféře. Výtěžky vždy přesáhly 50 % hm. a morfologické vlastnosti polymeru byly zachovány. Transformace polypyrrolových solí na odpovídající báze s následnou karbonizací byla sledována pomocí FTIR spektroskopie. Elementární analýza potvrdila následnou konverzi polypyrrolu na uhlík obsahující dusík. Specifické povrchy byly řádově desítky m(2) g(-1); zvýšily se z globulí na nanotrubice a nanovlákna, ale byly prakticky nezávislé na teplotě expozice. Vodivost prášků byla srovnávána s vodivostí pelet, pokud byla možná jejich příprava. Když se teplota zvýšila až na 400 °C, vodivost se u všech vzorků snížila o cca. 5 řádů, např. pro nanovlákna od 10 do 10(-4) S cm(-1), ale obnovena na 10(-1) S cm(-1) po následné karbonizaci až do 700 °C. Polypyrroly vystavené různým teplotám následně byly testovány na adsorpci organického barviva, Reactive Black 5, z vody. Adsorpce barviva na původních polypyrrolech silně závisela na morfologii polymeru. Polypyrrolová nanovlákna dokázala barvivo úplně odstranit s kapacitou 100 mg g(-1), zatímco adsorpce na polypyrrolové globule byla špatná. Adsorpční účinnost se tak zvýšila z globulí na nanotrubice a nanovlákna. Adsorpční výkon byl po karbonizaci snížen, ale obecné trendy byly zachovány.

Fabrication of adsorbents with excellent adsorption capacity, outstanding stability, easy separation ability, excellent recyclability and widely generality for organic dyes removal from wastewater remains challenging. Herein, three-dimensional polyaniline/poly(vinyl alcohol)/montmorillonite (PANI/PVAL/MMT) hybrid aerogels with easy separation performance and highly effective reusable adsorption on both anionic and cationic dyes were fabricated by a simple in-situ polymerization method. As-prepared hybrid aerogels were characterized via infrared and Raman spectra, scanning electron microscopy, energy dispersive spectra mapping, small and wide-angle X-ray scattering, thermogravimetric analysis, mercury intrusion porosimetry and elemental analysis. The results showed that MMT particles were successfully incorporated into aerogel matrix. Well-defined hierarchical structure, where PANI nanofibers are coated on the skeleton wall, can be observed for PANI/PVAL/MMT when the incorporation amount of MMT was around 11.1 wt%. The adsorption performance of as-prepared hybrid aerogels on both anionic and cationic dyes was systemically carried out at different solution pH, adsorbent dosage and initial dye concentration. The data analysis showed that the adsorption process for PVAL/PANI/MMT aerogel for Reactive Black 5, methyl orange and safranin followed Freundlich isotherm and the maximum experimental adsorption capacities were found to be 199, 251 and 57.0 mg g

Polypyrrole globules, nanofibers and nanotubes were activated by their carbonization at 650 °C in the 3:1 mass excess of molten potassium hydroxide in argon. They have been compared with parent polypyrroles and analogous samples obtained by the carbonization in the absence of hydroxide. The yields after activation, 12–18 wt%, were lower compared to the carbonization, which exceeded 50 wt%. The changes in molecular structure are discussed on the basis of FTIR and Raman spectra. One-dimensional morphologies, especially nanotubes, were superior to globules in most respects. They have higher conductivity close to 10 S cm−1, which was reduced by two orders of magnitude after arbonization but partly recovered after activation. The specific surface areas of nanotubes of the order of tens m2g−1 was several times higher compared with globules. They have not changed after carbonization but increased several times upon activation. The activated polypyrroles were tested as adsorbents of anionic azo dye, Reactive Black 5. Activated nanotubes performed the best in adsorption followed by parent nanotubes and nanofibers. The mechanism of dye adsorption is proposed by considering the presence of dye tautomers identified on the basis of FTIR spectra Polypyrrolové globule, nanovlákna a nanotrubičky byly aktivovány karbonizací při 650 °C v hmotnostním přebytku 3:1 roztaveného hydroxidu draselného v atmosféře argonu. Byly porovnány s původními polypyrroly a analogickými vzorky získanými karbonizací v nepřítomnosti hydroxidu. Výtěžky po aktivaci, 12–18 hm. %, byly nižší ve srovnání s karbonizací, která přesáhla 50 hm. %. Změny v molekulární struktuře jsou diskutovány na základě FTIR a Ramanových spekter. Jednorozměrné morfologie, zejména nanotrubice, byly ve většině ohledů lepší než globule. Mají vyšší vodivost blízkou 10 S cm−1, která se po karbonizaci snížila o dva řády, ale po aktivaci se částečně obnovila. Specifický povrch nanotrubic v řádu desítek m2g−1 byl několikanásobně vyšší než u globulí. Po karbonizaci se nezměnily, ale po aktivaci se několikrát zvýšily. Aktivované polypyrroly byly testovány jako adsorbenty aniontového azobarviva Reactive Black 5. Aktivované nanotrubice si vedly nejlépe v adsorpci následované mateřskými nanotrubičkami a nanovlákny. Mechanismus adsorpce barviva je navržen s ohledem na přítomnost tautomerů barviva identifikovaných na základě FTIR spekter

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&minus, 1), good thermal stability (in the range from 25 to 150 &deg, 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&ndash, 8.2 GHz). The nanostructures&rsquo, morphology and chemical structure were characterized by scanning electron microscopy, Brunauer&ndash, Emmett&ndash, 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.

Poly(aniline-co-p-phenylenediamine) cryogels stabilized by poly(vinyl alcohol) were prepared by one-step oxidative cryocopolymerization. Composite cryogels have macroporous structure with pore sizes up to tens of micrometers; however, copolymer cryogels have smaller pores compared to homopolymer cryogels. The cryogels containing 70 mol% and 80 mol% of aniline have the smallest pores and have the highest mechanical stability. The decrease in aniline fraction led to decrease of conductivity from 5×10–2 S cm–1 for polyaniline-based cryogel to

The blue thin polyaniline base film changes its color to green after immersion of the film into dibutyl phosphonate. The green color of the film converts to a greenish-blue after heating to 200 °C in air, which is characteristic for the protonated conducting form of polyaniline. This is in contrast to the "standard" polyaniline hydrochloride, which is transformed into a cross-linked polyaniline base under such conditions. To explain this unexpected observation, the interaction of polyaniline base with dibutyl phosphonate at ambient conditions and after heating to 200 °C was studied using UV-visible, FTIR and Raman spectroscopies. On the basis of these studies, we propose that the dibutyl phosphite tautomeric form of dibutyl phosphonate, which interacts with polyaniline base at 20 °C, converts to the oxidized form, dibutyl phosphate, at 200 °C and subsequently protonates the film. Quantum-chemical modeling of the interaction of polyaniline base with dibutyl phosphite and dibutyl phosphate supports this explanation.

Polypyrrole nanotubes rank among the most conducting forms of organic semiconductors. They are prepared by the oxidation of pyrrole in the presence of methyl orange. Other organic dyes, viz. ethyl orange, Acid Blue 25, and Acid Blue 129, have been used in the present study to prepare globules or nanofibers. The resulting polypyrroles were studied in detail by Raman spectroscopy. The apparent paradox when a dye contribution to spectra is absent with 785 nm excitation line and present with shorter wavelengths is explained by the resonance character of the Raman scattering, which allows the separation of the contributions from the polypyrrole surface and from the bulk. These differ depending on the laser excitation wavelength and the position of absorption maximum of the individual dyes in ultraviolet-visible spectra and affect both the laser-penetration depth and observation of the resonance effect. The spectra are discussed in terms of different ordering of polymer chains in individual morphologies. The correlation between conductivity, surface areas, and the proportions of ordered and disordered polypyrrole phases at the surface and in the interior of nanostructures is proposed and established using resonance Raman spectroscopy.

Polypyrrole/molybdenum disulfide (PPy/MoS2) composites were synthesized by in-situ chemical polymerization of pyrrole in the presence of MoS2 flakes. The conductivity of the composite with a moderate content of PPy (15–30 wt%) reached 13 S cm−1, which is markedly higher than the conductivity of both the pristine PPy and MoS2, 1 and 10−6 S cm−1, respectively. The improved conductivity was explained by the formation of ordered thin PPy films with high conductivity at the MoS2 surface. At higher pyrrole content, globular PPy was formed in the bulk of the composite resulting in an increase of a disordered polymer fraction, and the conductivity decreased. The composite conductivity is thus controlled not only by content of PPy but also by the proportions between ordered and disordered PPy phases. The structural and morphological characterization of composite materials is based on Fourier-transform infrared and Raman spectroscopies, wide-angle X-ray diffraction, and scanning and transmission electron microscopies. The charge-carrier transport in the composites fits the Mott variable-range hopping mechanism.

Macroporous open-cell melamine sponges were coated with a conducting polymer, polypyrrole, during in-situ oxidative polymerization of pyrrole. Two samples, differing in polypyrrole content, 8.2 and 27.4 wt%, were prepared. They were exposed to various temperatures up to 700 °C in an inert atmosphere. The macroporous structure and mechanical integrity were preserved after this process. This converted both the polypyrrole coating and the melamine sponge to macroporous nitrogen-containing carbons. The changes in molecular structure in the course of carbonization were followed by elemental analysis and FTIR and Raman spectra. The specific surface area of polypyrrole-coated sponge increased from ca. 90 to ca. 300 m2 g−1 along with accompanying increase in the porosity. The conductivity of the sponges was recorded as a function of compression in a newly developed apparatus. The sponge containing 27.4 wt% pyrrole had conductivity of the order of 10−2 S·cm−1 at 0.1 MPa pressure, which was reduced by four orders of magnitude when exposed to 400–500 °C and nearly recovered after the temperature reached 700 °C. The sponges were tested in electromagnetic radiation shielding and displayed both radiation absorption and, to a lower extent, radiation reflection proportional mainly to the samples’ conductivity.

Polypyrrole has been prepared by facile single-step chemical oxidative polymerization of the monomer in aqueous medium containing an anthraquinone dye, Acid Blue 25 or Acid Blue 129. The addition of the former structure-guiding agent results in the formation of polypyrrole nanowires with conductivity improved up from the units S cm–1 to 60 S cm−1. The second closely related dye, Acid Blue 129, had no impact on polymer morphology but in its presence the conductivity of polypyrrole also increased. It has been shown that the pyrrole concentration and oxidant-to-pyrrole mole ratio significantly affect the conductivity of synthesized polypyrrole. Polypyrroles have been characterized by FTIR and Raman spectroscopies to assess their molecular structure and intermolecular interactions. Considering the applications in biomedicine, the cytotoxicity of the samples has also been tested. Polypyrrole prepared with Acid Blue 129 has significantly lower cytotoxicity compared to that prepared with Acid Blue 25. The cytotoxicity of both polypyrroles can be eliminated by purification step. Low cytotoxicity combined with high conductivity enables application of these conducting polymers in biomedicine.

Aim of this study is to bring systematic comparison of structure and properties of the redox-active oxidation products of various phenylenediamines prepared under various acidic conditions. According to literature, structure and properties of the phenylenediamine oxidation products depend on the reaction conditions. Various ladder-like structures have widely been accepted in the literature since they can be potentially created from any phenylenediamine isomer. The presence of polyaniline-like structural units, however, has also been reported and often discussed. The conductivity of the reaction products was compared for the oxidation of o-, m- and p-phenylenediamine with ammonium peroxydisulfate in 1 M methanesulfonic acid, water, or in 1 M ammonium hydroxide. The combination of size exclusion chromatography with UV–visible, FTIR and Raman spectroscopies allow us to analyze the molecular structure of the oxidation products and to bring significant information on (1) the formation of oligomer and polymer fractions, (2) the content of benzenoid and quinonoid units suggesting the presence of polyaniline-like segments, and (3) the participation of phenazine-like constitutional units indicating the formation of polycyclic structures. The oxidation products have also been tested for their cytotoxicity in order to estimate their application potential in biomedicine. The dilution of extracts below 5% concentration was generally needed to suppress the cytotoxicity.

A low-molecular-weight organic semiconducting material was prepared by the redox interaction between pyrrole and p-benzoquinone. The reaction between pyrrole and p-benzoquinone in aqueous solutions of methanesulfonic acid proceeded smoothly at room temperature. The product with a globular morphology obtained in high yield in 0.1 M methanesulfonic acid had the highest conductivity, 4.6 × 10−6 S cm−1. On the other hand, the samples prepared in the absence of acid or at high acid concentration were non-conducting. EPR spectroscopy confirmed the presence of electronic species as charge carriers responsible for conductivity. The dominating component was proved to be a low-molecular-weight adduct composed of the quinhydrone complex and the pyrrole molecule. FTIR and Raman spectra were used to discuss the molecular structure in detail. A strong electrorheological effect with a very fast response time was demonstrated by the reproducible increase in the viscosity of suspensions in silicone oil after application of the electric field. The effect is discussed with the help of dielectric spectroscopy.

The impact of various sterilization methods on the conductivity of polyaniline and polypyrrole has been tested. The sterilization methods included β- and γ-irradiation, UV-light irradiation, immersion in aqueous ethanol, and moist and dry heat treatment. Except for the dry heat, all methods can be used for the sterilization of conducting polymers without any significant reduction in their conductivity. Any changes in the conductivity associated with the modified molecular structure due to polymer deprotonation are discussed with the help of FTIR spectroscopy. The morphology of conducting polymers has not been affected by the sterilization.

Non-thermal plasma has proved its benefits in medicine, plasma assisted polymerization, food industry and many other fields. Even though, the ability of non-thermal plasma to modify surface properties of various materials is generally known, only limited attention has been given to exploitations of this treatment on conductive polymers. Here, we show study of non-thermal plasma treatment on properties of globular and nanostructured polypyrrole in the distilled water. We observe that plasma presence over the suspension level doesn’t change morphology of the polymer (shape), but significantly influences its elemental composition and physical properties. After 60 min of treatment, the relative concentration of chloride counter ions decreased approximately 3 and 4 times for nanostructured and globular form, respectively and concentration of oxygen increased approximately 3 times for both forms. Simultaneously, conductivity decrease (14 times for globular and 2 times for nanostructured one) and changes in zeta potential characteristics of both samples were observed. The modification evolution was dominated by multi-exponential function with time constants having values approximately 1 and 10 min for both samples. It is expected that these time constants are related to two modification processes connected to direct presence of the spark and to long-lived species generated by the plasma.

Molybdenum and tungsten sulfides are semiconducting materials with flake-like morphology. Their applicability in electrorheological suspensions was enabled by the coating with a conducting polymer, polyaniline, after its conversion to non-conducting polyaniline base. For instance, the conductivity of tungsten sulfide, 0.056 S cm−1, increased to 0.98 S cm−1 after coating with polyaniline, and was conveniently reduced to 6.3 × 10−6 S cm−1 after conversion to polyaniline base. Such approach reduces the potential current drifts in electrorheological suspensions and allows for the application of sulfides in electrorheology. The optical microscopy demonstrated the formation of particle chains in silicone-oil suspensions after application of electric field. The electrorheological performance was assessed by the measurement of viscosity on the shear rate in the absence and in the presence of electric field and it is discussed on the bases of dielectric spectra.

The process of ageing of polypyrrole is accompanied by gradual changes in its chemical composition, protonation level and charge transport mechanism. Although these changes are often limiting for practical application of polypyrrole, they are still far from being understood. In our contribution, natural ( i.e. ageing at room temperature) and accelerated ageing (at 120 °C) of polypyrrole nanotubes were studied. Natural ageing for about 3 year timespan lead to relative decrease of sample conductivity to about 0.2 of its initial σ 0 value. Accelerated ageing caused a dramatic decrease of 7 orders of magnitude after about 1000 h accompanied by partial deprotonation and backbone oxidation as confirmed by infrared, Raman and XPS spectroscopy and elemental analysis. Occurrence of crystalline domains was attributed to residual methyl orange and was not affected by ageing. The presence of methyl orange was found crucial for improving stability of sample conductivity; it caused about 4 orders of magnitude enhanced conductivity when compared with polypyrrole without methyl orange. In macroscopic scale the conductivity loss was found to be a spatially homogeneous process as revealed by electrical tomography. With increasing ageing time, besides gradual degradation on microstructural level, a qualitative change of charge transport mechanism was found.

Polyaniline (PANI) is conducting when doped, typically with an acid. However, acids are not the only species able to dope PANI. In this study, we show that non-conducting PANI base powder interacts with dimethyl H-phosphonate (DMPH), diethyl H-phosphonate (DEPH), dibutyl H-phosphonate (DBPH) and diphenyl H-phosphonate (DPPH) and yields conducting adducts; the highest conductivity 0.23 S cm −1 is observed for DPPH. The samples were analyzed by FTIR, Raman, NMR, and EPR spectroscopies. We have shown that the doping of PANI with H-phosphonates is only partial and at least part of DEPH and DPPH molecules preserves the H-phosphonate structure, in contrast with DMPH and DBPH. We have also correlated the information on polaron delocalization and mobility obtained from Raman and EPR spectra – polarons in the PANI adduct with DEPH and DPPH have higher mobility. This paper represents a comparative study of a class of PANI-based materials and shows a connection between chain conformation of PANI and materials properties.

Polyaniline/polybenzimidazole (PANI/PBI) blend membranes with various ratios of PANI/PBI were prepared by the solution casting method. The resulting free-standing membranes were subsequently doped with hydrochloric acid. In the next step, the membranes were heated up to 600 °C in an inert nitrogen atmosphere. FTIR spectroscopy and Raman scattering show the conversion of the blend to a nitrogen-containing carbon-like material. The permeability and sorption properties with respect to H 2 , O 2 , N 2 , CH 4 , and CO 2 were determined. The separation qualities of the thermally treated PANI/PBI blend membranes significantly exceed those of non-thermally treated membranes. The permeation properties show a strong dependence on the PANI concentration in the blend and on its doping. The best separation performance for H 2 /N 2 , CO 2 /N 2 , and CO 2 /CH 4 is obtained with the thermally treated undoped PANI/PBI 20/80 blend membrane.

Non-conducting polyaniline base interacts with organic phosphites to a conducting product resembling classical polyaniline salts. Polyaniline–phosphite complexes were carbonized in inert atmosphere at 650 °C to phosphorus- and nitrogen-containing carbons. The resulting materials were tested with respect to their electrochemical performance by considering their capacitive properties and electrocatalytic activity towards oxygen reduction reaction (ORR). Carbonized polyaniline–diphenyl phosphite displayed the highest capacitance among all investigated carbons, reaching the values above 100 F g −1 at 5 mV s −1 in concentrated potassium hydroxide solution, while the same material also displayed the highest ORR activity in alkaline media. Considering small specific surface area of obtained carbon materials, the synthetic procedures lead to the surface structures which are exceptionally active for charge storage and in electrocatalysis of ORR. It is proposed that further improvement of electrochemical properties can be obtained by preserving the type of the present surface functional groups with simultaneous increase of their number by the increase of the specific surface.

The synthesis of polypyrrole nanotubes using methyl orange as a structure guiding agent is a popular method for obtaining electrically conductive material of nanostructured morphology. This work presents certain route of chemical synthesis, where the experimental conditions were optimized in order to obtain a material with high conductivity (up to 91.6 S cm −1 ) and specific surface area (up to 67.6 m 2 g −1 ) via modification of two parameters: a) the methyl orange concentration (from 0.5 mM to 25 mM) and b) the polymerization temperature (from −5 °C to 35 °C). The synthesized material was then characterized by scanning electron microscopy, energy X-ray dispersive spectroscopy, nitrogen physisorption, Fourier-transform infrared and Raman spectroscopies and measurement of electrical conductivity. It was found, that the concentration of methyl orange in polymerization solution strongly influences both the diameter (ranging from 60 to 900 nm) and the shape (circular or rectangular cross-section) of synthesized polypyrrole nanotubes. Moreover, while at low concentrations of methyl orange in the native liquor the resulting nanotubes are accompanied by globular form of polypyrrole, at higher concentrations the composite of polypyrrole nanotubes with acidic form of methyl orange is produced. The detailed mechanism of methyl orange role during the polymerization process was explained in terms of behaviour of planar aromatic sulfonic acids. As for the polymerization temperature, it has stronger influence on the morphology than on the chemical composition of resulting polypyrrole nanotubes. Finally, we report a universal relation – a power law describing dependency of electrical conductivity on nanotube diameter for this class of materials.

Polyaniline is a conducting polymer with an application potential in the field of biomedical engineering. By employing FTIR spectroscopy and conductivity measurements, it has been shown that the oxidation at stoichiometric peroxydisulfate-to-aniline mole ratio 1.25 in the solutions of formic acid in the range 0–10 M provides samples of a moderate conductivity of the orders 0.01–0.1 S cm−1. They consist of polyaniline and aniline oligomers as typical of the aniline oxidation in weak acids. The detailed investigation of the infrared spectra indicates a partial ring-carboxylation of polyaniline at high acid concentrations. The extent of structural defects is higher for a series prepared at over-stoichiometric peroxydisulfate-to-aniline mole ratio 2.5, which provided only non-conducting samples. The reference sample series represented by poly(aniline-co-o-aminobenzoic acid) was also prepared and is used in the discussion of the infrared spectra.

Poly(aniline- co -1,3-phenylenediamine) cryogels were prepared by a simple one-step approach involving oxidative cryopolymerization of respective comonomers in the presence of poly(vinyl alcohol) stabilizer. Resulting cryogels were characterized by SEM, Raman spectroscopy, conductivity and tensile measurements. The addition of small amounts (1 mol%) of 1,3-phenylenediamine into copolymerization with aniline allows for the significant increase of cryogel pore sizes without substantial change in conductivity and mechanical stability. This is the important parameter for future use of such composites cryogels in biomedicine and electrochemistry.

Nitrogen-containing carbon derivatives were prepared by the carbonization of poly(aniline-co-p-phenylenediamine) cryogels in inert atmosphere. Lower aniline fraction in the comonomer mixture used for preparation of the cryogels led to the decrease of their thermal stability, a consequent increase of carbonization degree, and less defective structure of carbonized materials. The resulting carbonaceous products had up to 4 orders of magnitude higher specific surface area than their respective cryogel precursors, the highest value 931 m2 g&minus, 1 being achieved for carbonized poly(p-phenylenediamine) cryogel. Electrochemical characterization of the carbon derivatives demonstrated that the decrease in aniline concentration during the synthesis of the precursor cryogels led to higher gravimetric capacitance for corresponding carbonized materials. These materials can potentially be used for energy storage applications.