Preparation and properties of conducting polypyrrole-sulfonated polycarbonate composites

The electrically conducting composites are prepared by chemical oxidative polymerization using polypyrrole (PPy) and polycarbonate (PC) or sulfonated polycarbonate (SPC) in chloroform. The pyrrole was protonated and polymerized using iron(III) chloride (FeCl₃). The sulfonic group was introduced into the structure of PC in order to enhance the coulombic interaction between each phase of composites. The electrical conductivity and morphology were observed as a function of the amount of PPy. The electrical conductivity was increased up to 0.82 S/cm with the amount of PPy. The PPy/SPC composites were stable in atmosphere.     

Free-standing,conducting films of pyrrole/N-(4-ferrocenylbutyl-)pyrrole benzenesulphonate copolymers

The electrochemical preparation, in a flow-through cell, of self-supporting films of a pyrrole/N(ω-ferrocenylbutyl-)pyrrole copolymer with benzebesulphonate as a dopant anion is described. For comparison, polypyrrole benzenesulphonate was made under the same conditions. The polymer films were characterized by complete elemental analysis, i.r. spectroscopy, conductivity at various film potentials, scanning electron microscopy and dynamic elastic modulus measurements and their temperature dependence. Copolymerization is shown to be a viable method for producing redox-modified polypyrrole films when moderate conductivity and limited mechanical strength are acceptable.     

An FTIR study of the role of H2O and D2O in the aging mechanism of conductive polypyrroles

In the present work the role of H₂O was studied by conductivity measurements and FTIR spectroscopy using the isotopic effect of deuterium in order to elucidate the aging mechanism of conductivity of polypyrroles. Polypyrrole was prepared with PTS as a dopant, by using deuterated water. Conductivity measurements showed changes due to structural water and atmospheric humidity. The FTIR absorption spectra indicated that the most probable structure of polypyrrole is the two-dimensional one. This finding could be attributed to the inhibition of polypyrrole’s IR modes. The infrared spectrum analysis show that the γ-NH bending mode of pyrrole has significantly changed after polymerization of pyrrole and this result is in accordance with XPS measurements.     

Conductive composites from polyvinyl alcohol and polypyrrole

The electrochemical polymerization of pyrrole on a platinum electrode covered with a film of polyvinyl alcohol produces black, flexible films which are a composite of polypyrrole and polyvinyl alcohol. These composites incorporate some of the attractive electrical properties of the polypyrrole and some of the attractive mechanical properties of the polyvinyl alcohol.     

Synthesis and characterization of polypyrrole/TiO2 composite by in situ polymerization method

Polypyrrole/TiO₂ composite is prepared by in situ polymerization of pyrrole on the TiO₂ template. The TiO₂ microbelts are prepared by sol–gel method using the absorbent cotton template for the first time. Then the TiO₂ microbelts are used as template for the preparation of polypyrrole/TiO₂ composites. The structure, morphology and properties of the composites are characterized with scanning electron microscope (SEM), IR and Network Analyzer. A possible formation mechanism of TiO₂ microbelts and polypyrrole/TiO₂ composites has been proposed. The effect of the molar ratio of pyrrole/TiO₂ on the photocatalysis properties and microwave loss properties of the composites is investigated.     

Optimum reaction conditions for the polymerization of pyrrole by iron(III) chloride in aqueous solution

The optimum initial mole ratio of iron(III)/pyrrole for the polymerization by aqueous iron(III) chloride solution at 19°C is shown to be approximately 2.38 ± 0.04. Thus the number of electrons transferred per pyrrole ring in the chemical synthesis of polypyrrole is consistent with values quoted for various electrochemical syntheses. It is shown that changing the initial mole ratio of the reactants affects the yield but not the chemical composition or conductivity of the polypyrrole powders. The extent of reaction as a function of time at two different reactant concentrations is also presented.     

Room temperature synthesis of Ag/polypyrrole core–shell nanoparticles and hollow composite capsules

Two kinds of Ag/polypyrrole composite nanoparticles have been prepared via a one-step redox reaction between silver nitrate and pyrrole monomer at room temperature. One is Ag@polypyrrole core–shell nanoparticles that were synthesized by making use of synergic inducing effect of polyvinyl pyrrolidone and p-toluenesulfonic acid existing in aqueous solutions. The other is AgCl@Ag/polypyrrole core–shell composite nanoparticles that were synthesized in the presence of HCl using the in situ-formed AgCl particles as the template. For the latter, its core can be easily removed via a simple dissolving procedure in sodium hyposulfite or ammonium chloride aqueous solutions, obtaining the Ag/polypyrrole hollow composite capsules. Experimental results suggest that the shell thickness and core diameter of the resulting composites can be controlled expediently by adjusting reaction time and concentration of pyrrole monomer.     

Electrical properties and stability of polypyrrole containing conducting polymer composites

Conducting polymer composites of polyethylene and polypyrrole (PE/PPy), polypropylene and polypyrrole (PP/PPy), and poly (methyl methacrylate) and polypyrrole (PMMA/PPy) were prepared by means of a chemical modification method, resulting in a network-like structure of polypyrrole embedded in the insulating polymer matrix. The content of polypyrrole determined by elemental analysis varied from 0.25 to 17 wt.%. Electrical conductivity of compression-moulded samples depends on the concentration of polypyrrole and reached values from 1 × 10⁻¹¹ to 1 S/cm. The morphology of the composites was investigated by low-voltage scanning electron microscopy (LVSEM). Potential contrast measurements as a function of the acceleration voltage were used to prove the perfection of the PPy network structure. The electrical transport mechanism in PP/PPy composite was studied. The data of the temperature dependence of conductivity were fitted following the function for a charge-energy-limited tunnelling (CELT) model. There is only a small drop in conductivity caused by annealing of PP/ PPy composites in air at temperatures up to 80 °C. A stabilizing effect of PPy on thermal stability of polypropylene is shown by thermogravimetric analysis. The antistatic properties of PE/PPy and PMMA/PPy composites were demonstrated.     

The effect of monomer and clay proportion on the formation of polypyrrole clay intercalated nanocomposite

In this study, intercalated polypyrrole/montmorillonite nanocomposite was synthesized by a facile and simple solution intercalation method. The method is based on the exchanging of pyrrole monomers with sodium interlayer cations followed by polymerization by adding ammonium persulfate as oxidant. To avoid the spontaneous polymerization of pyrrole outside the clay, the proportions of pyrrole to clay and that of monomer to oxidant were varied. Several techniques have been used to study the structure and conductivity of the obtained materials: Fourier transform infrared spectroscopy, X-ray diffraction, Energy-dispersive X-ray spectroscopy analysis, scanning electron microscopy, Brunaner–Emmet–Teller technique, impedance spectroscopy and ultraviolet–visible spectroscopy. It was shown that it is not necessary to subject clay to organophilation with quaternary alkylammonium or to ultrasonic activation, or to treat it thermally to form intercalated nanocomposite. By increasing the amount of clay to that pyrrole, an intercalated polypyrrole clay nanocomposite is formed. Theevidence of the intercalation of polypyrrole is deduced from the X-ray diffraction and the Brunaner–Emmet–Teller technique specific surface. Both the expansion of the basal interlayer distance to 14 Å and the decrease of the specific surface area from 78.2 for the clay to 48 m² g^–1 prove the formation of an intercalated structure. The conductivity has been measured using impedance spectroscopy. The dc conductivity was in the range of 2–10^–3 S/cm.     

Electronic and magnetic properties of polypyrrole films depending on their one-dimensional and two-dimensional microstructures

We report on the electronic and magnetic properties of polypyrrole films with a one-dimensional and two-dimensional microstructure. Polypyrrole films as well defined and stable polymers are studied. The aim of this work is an explanation of the macroscopic conductivity based on microscopic and electronic structure. In particular we attribute the high d.c. conductivity, the frequency-independent a.c. conductivity and the weak temperature dependence of the conductivity to the existence of two-dimensional crosslinked areas. We characterize the polypyrrole films by photoelectron spectroscopies (X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS)), by electron paramagnetic resonance (EPR) spectroscopy, and by the frequency- and temperature-dependent conductivity measurements. We compare the results to the corresponding properties of one-dimensional polypyrrole films. The two-dimensional films consist of a graphitic electronic structure in which pyrrole monomers either contribute to the two-dimensional π-system or maintain their monomeric character, as characterized by photoelectron spectroscopies. The EPR data reveal magnetic centers that show a Curie-like susceptibility and a weak Pauli contribution, and the latter does not contribute to the conductivity mechanism. The EPR linewidth is extraordinarily sharp and reversibly reflects the dynamics of the interaction to oxygen.     

“Switching effect” in pressure deformation of silicone rubber/polypyrrole composites

Conductive silicone rubber/polypyrrole composites were prepared by cast molding of polymer matrix components and chemically synthesized polypyrrole (PPy). Composites contained from 2.2 to 8.5 vol.% of PPy. The sigmoid dependence of the conductivity of original uncompressed sample on the filler was found and PPy percolation threshold concentration lower than 4 vol.% was estimated.Electrical conductivity of silicone rubber/polypyrrole composites in pressure deformation showed a steep decrease more than five orders of magnitude to values corresponding to an insulator. This “switching effect” had a good reproducibility, which suggests a possible use of this material in microelectronics.     

Electrochemical preparation and characterization of polypyrrole doped with bis(trifluoromethanesulfone) imide anions

Polypyrrole-bis(trifluoromethanesulfone)imide, PPy-TFSI, thin film electrode was prepared electrochemically by potential cycling or galvanostatically at a platinum electrode from a 0.5 M pyrrole/ 0.1 M lithium bis(trifluoromethanesulfone)imide, LiTFSI, /acetonitrile solution. The TFSI anion was selected as a dopant for polypyrrole because previous studies have shown that such polymer has a high electrical conductivity. The resulting PPy-TFSI film electrodes were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The apparent redox potential for a TFSI-doped polypyrrole film is slightly shifted to more positive potential in comparison to a perchlorate-doped film. This is related to the high delocalization of the charge of the TFSI anion which results in weaker anion–cationic polymer coulombic interactions. The low frequency capacitance and ionic resistance of the TFSI-doped polypyrrole are comparable to those reported for other polypyrrole film electrode.     

Polypyrrole microstructure deposited by chemical and electrochemical methods on cotton fabrics

Electrochemically and chemically coated cotton fabrics with polypyrrole are comparatively evaluated and characterized in order to produce the conducting fabrics/textiles. The polypyrrole coated fabric is obtained electrochemically by constant current electrolysis (2 mA cm⁻²) at room temperature for 4 h. The stability, electrical conductivity and electrochemical behaviour of such composite coating are evaluated by means of SEM, FTIR, TGA, DSC, four-probe conductivity, impedance spectroscopy and cyclic voltammetry. When compared to chemical method thicker films of polypyrrole with globular microstructure could be obtained by electrochemical technique and the conductivity of the polypyrrole film was also high (1.9 × 10⁻² to 3.3 × 10⁻¹ S cm⁻¹). The weight uptake and the electrical conductivity of the coated fabric increase with concentration of pyrrole and time of electrolysis. Many other physico-chemical properties of the polypyrrole films obtained by the two methods were found to be qualitatively similar.     

Polypyrrole/MWNT nanocomposites synthesized through interfacial polymerization

Polypyrrole/carbon nanotubes (CNTs) composites were synthesized by dispersion of organically modified multiwall carbon nanotubes during an interfacial polymerization of pyrrole. During the polymerization, the carbon nanotubes are entrapped by the polymer chains and the nanocomposite is formed in the interphase between two immiscible solvents. The method favours a better dispersion of the nanotubes in the polypyrrole offering enhanced electrical properties. The characterisation of the composite material has been established by XRD, TGA analysis and electron microscopy techniques.     

The preparation and properties of sodium and organomodified-montmorillonite/polypyrrole composites: A comparative study

Two montmorillonites, an inorganic sodium montmorillonite (NaMMT) and an organo-modified montmorillonite (OMMT), were used for the preparation of montmorillonite/polypyrrole (MMT/PPy) composites. MMT particles were modified by the in situ polymerization of pyrrole in water, in aqueous solution of dodecylbenzenesulfonic acid (DBSA) used as anionic surfactant, and in water/methanol. Ferric chloride was used as oxidant in each case. Wide angle X-ray scattering (WAXS) measurements proved the intercalation of PPy into the galleries of NaMMT regardless the reaction media. In contrast, for OMMT/PPy composites, the increase of interlayer spacing depends on the preparation conditions, the highest increase in interlayer spacing was achieved in water/DBSA solution. The WAXS patterns of OMMT/PPy composites synthesized in methanol/water showed no change in interlayer spacing and the electrical conductivity of these composites was low, similar to that of NaMMT/PPy composites prepared under the same conditions. Conductivity about 1.1 S cm⁻¹ was reached for OMMT/PPy composites containing 13.3 wt% PPy prepared in the presence of DBSA. The NaMMT/PPy composite containing 15.6 wt% PPy and prepared under the same conditions showed a conductivity of 0.26 S cm⁻¹. X-ray photoelectron spectroscopy (XPS) proved that the surface of NaMMT/PPy composites is rich in MMT, whereas more PPy was found on the surface of OMMT/PPy composites. The conductivity of composites correlated with the N/Si atomic ratio determined from XPS results, which was taken as a semi-quantitative measure of the PPy surface fraction.     

Vapour phase polymerisation of pyrrole on cellulose-based textile substrates

Conducting textiles were prepared embedding polypyrrole in natural and man made cellulose-based fibres, such as cotton, viscose, cupro and lyocell, by means of in situ polymerisation. Chemical vapour phase deposition of polypyrrole is a suitable process for producing electro-conductive composites in two steps: (a) fabric impregnation with an aqueous solution of oxidant and dopant and subsequent drying; (b) exposition to pyrrole vapour and polymerisation.Comparative morphological and structural analysis was carried out on the conducting viscose prepared with both vapour and liquid phases processes and some significant differences in the structural, calorimetric and electrical properties were highlighted, due to the different methods of preparation. Vapour phase prepared fabrics show a high uniform polypyrrole coating on the fibre surface and its partial penetration inside the amorphous zones of the fibre bulk.WAXD analysis shows that the conducting fabrics preserve the crystalline structure of the cellulose matrix, while SAXS results evidence the presence of a nanoparticle dispersion of polypyrrole in the cellulose matrix. Polypyrrole–cellulose conducting composite textiles show good performances to light exposure and washing fastness tests.     

Chemical in situ polymerization of polypyrrole on bacterial cellulose nanofibers

Conducting porous nanofibrous composite membranes of bacterial cellulose (BC) and polypyrrole (PPy) were prepared through in situ oxidative chemical polymerization of pyrrole (Py) on the surface of synthetized BC nanofibers by using FeCl₃ as oxidant agent. The influence of polymerization conditions on electrical conductivity, morphological and thermal stability of the BC/PPy composites was investigated. The amount of PPy deposited on the BC nanofibers increased with increasing the monomer concentration and reaction time while the electrical resistivity of the composites decreased due to the formation of a continuous layer that coated the nanofiber surface. Fourier transform infrared (attenuated total reflectance mode) spectroscopy (FTIR-ATR) of the composites revealed strong interaction between PPy and BC, as characterized by a blue-shift of C–N band of PPy towards pure PPy with increasing Py concentration. BC/PPy composites showed higher thermal stability than BC membrane due to the protective effect of the conducting polymer coating. Scanning electron microscopy (SEM) analysis of the composites revealed that PPy consisted of particles of mean size of 35 nm that form a continuous coating that fully encapsulates the BC nanofibers. The material properties obtained by the method described in this work for the BC/PPy composites open interesting possibilities for novel applications of electrically conducting bio-based composites, particularly those that may exploit the biocompatible nature of the BC/PPy membranous composite.     

Polypyrrole-carbon nanotube composite films synthesized through gas-phase polymerization

Polypyrrole-carbon nanotubes (CNTs) composite films, having high conductivity and uniformity, were directly synthesized by depositing polymerization in the gas-phase. The conductive polypyrrole was filled as a matrix material between the CNT networks by self-organization of the pyrrole monomer. Compared to the traditional composite technique and film-coating procedures, this process can be largely increased the carrier mobility for electrical conductivity because act to conducting bridge connecting PPy, increased the conductivity up to five times, and simultaneously improved the thermal stability. The characterization of the composite film was established by TEM, XRD, TGA, and IR/Raman spectroscopic analysis.     

Polypyrrole composites for shielding applications

This article highlights the physical properties of polypyrrole (PPy) coated over MnZn ferrite (MZF), nickel coated over PPy, and PPy coated over Ni-MZF magnetic core particles. The commercial ferrite and Ni-ferrite particles are primarily used, and the PPy-ferrite particles with composite structure are synthesized both via an oxidative polymerization of pyrrole in an aqueous solution, which contains well-dispersed ferrite particles, and electrochemical polymerization technique in acetonitrile (ACN). The materials have been processed in the form of coatings, films, and sheets by blending of conventional polymer such as polyurethane (PU) wherein the composites retain the mechanical properties of the conventional polymers and the electrical conductivity of the conducting polymers. The influence of ferrite content with respect to the electrical and ferromagnetic properties of PPy composites were investigated by electrochemical impedance spectroscopy (EIS) and dc field-cooled, zero-field cooled susceptibilities and M–H loop measurements. Their structural characterization is also discussed based on Fourier transform infrared (FTIR) and the X-ray diffraction (XRD) measurements. The shielding effectiveness (SE) properties will be reported in our future studies.     

Electrical properties of pyrrole and its copolymers

Electrochemically prepared polypyrrole films have metallic conductivities in the range 40–100 S cm^?1 whereas poly-N-methyl pyrrole films have conductivities more typical of a semiconductor, t/if 10^?3 S cm^?1. Films made by the electrochemical polymerization of mixtures of pyrrole and N-methyl pyrrole have redox potentials intermediate between those of either monomer, indicating that they are in fact random copolymers. The electrical conductivity and thermopower measured as a function of copolymer composition show no evidence for an abrupt metal-semiconductor transition. All these polymers are stable in air to temperatures in excess of 100°C.