Chemical polymerization of pyrrole with disulfide structure and the application to lithium secondary batteries

An intramolecular cyclic disulfide-containing polypyrrole was prepared by the chemical-oxidative polymerization of 4,6-dihydro-1H-[1,2]dithiino[4,5-c]pyrrole (MPY), and the electrical properties were investigated as the cathode active material in lithium secondary batteries. Oxidizing agents and solvents for the chemical-oxidative polymerization were examined to prevent over-oxidation of the polypyrrole backbone. The conductivity of poly(MPY), the polymer prepared using FeCl₃ in ethylene glycol, was around 10⁻⁴ S/cm. Poly(MPY) showed very little over-oxidation, good redox properties, and a high discharge capacity of 398 mAh/g based on the redox response of the disulfide.     

Chemical oxidative polymerization of dodecylbenzenesulfonic acid aniline salt in chloroform

Polymerizations of dodecylbenzenesulfonic acid aniline salt (DBSAn) in chloroform using various electron acceptors were studied as a function of polymer yield and conductivity. Dichlorodicyanobenzoquinone (DDQ) is an effective oxidant for the polymerization of DBSAn to yield sufficient amount of polyaniline. Suspension polymerization of DBSAn in chloroform with a small amount of water containing ammonium persulfate (APS) as an oxidant was found to yield a homogeneous transparent and green-black suspension containing polyaniline. Polyaniline was found to exhibit strong solvatochromism in aqueous and chloroform solutions.     

Theoretical study of polymerization of pyrrole

The polymerization process of pyrrole has been theoretically studied using the semiempirical molecular orbital (MO) method. As a model for the polymerization, particularly representing the initial-stage reaction near the anode of the electropolymerization system, the dimerization of pyrrole is examined by the process of coupling of two cationic monomer radicals in two specifically different ways, i.e., via the σ-radical or via the π-radical. Furthermore, some related calculations are undertaken in connection with the reactions between cationic monomer and dimer radicals, and between a neutral monomer and a cationic monomer radical.     

Water-dispersed polypyrrole nanospheres via chemical oxidative polymerization in the presence of castor oil sulfate

The castor oil sulfate (COS), produced by the sulfonation of the castor oil (one of the most promising renewable sources), was used as both the surfactant and the dopant in the chemical oxidative polymerization of pyrrole. The resulting castor oil sulfate doped polypyrrole nanospheres (PPy/COS) were characterized with FTIR, UV–vis, TGA, zeta potentials and TEM techniques. It was found that their diameter decreased and their dispersing stabilities in water increased with the increasing of feeding ratio of COS. The PPy/COS nanospheres possess high electrical conductivity at room temperature and the weak temperature dependence of the conductivity.     

The formation of oligomers in the electrolyte upon polymerization of pyrrole

Pyrrole was polymerized by electrochemical and chemical oxidation of a solution of pyrrole and p-toluene sulfonic acid in acetonitrile. We have investigated the components formed within that electrolyte solution during the polymerization. Both, UV–VIS spectroscopy and size exclusion chromatography give evidence that pyrrole oligomers nP (n≤30) are formed in the solutions during the polymerization process. A model is proposed in which these oligomers act as intermediates of the polymerization reaction. Within that model the deviations from Faradayic behaviour at elevated current densities are explained. It also rationalizes the fact that polymer films with completely different properties can be realized by varying the experimental parameters.     

Polyaniline nanocomposites via chemical oxidative polymerization in the presence of functional MCM-48 as in situ dopant

Functional MCM-48 (F-MCM-48), prepared by anchoring the organic sulfonic acid on the surface of the 3D cubic (Ia3d) structural MCM-48, was used as both the inorganic substrate and the in situ dopant for the in situ chemical oxidative polymerization of aniline to obtain the PANI/F-MCM-48 nanocomposite material. The morphology of the resultant composite was characterized by SEM and a raspberry-like morphology was observed. The results of spectral analyses showed that there was a strong interaction between PANI chains and F-MCM-48, and the doping degree of PANI was high. Small-angle X-ray diffraction (XRD) analysis confirmed that the main peaks of the PANI/F-MCM-48 composite was similar to the pristine MCM-48, which revealed that the structure of MCM-48 was well-maintained after the polymerization and the resultant composite is more ordered and uniform than bulk PANI. Thermal gravimetric analysis (TGA) displayed that the thermal stability of the PANI/F-MCM-48 composite was enhanced, which could be attributed to the effect of F-MCM-48 acting as the shelter for the degradation of polyaniline chains. Moreover, the PANI/F-MCM-48 composite was possessed of good conductivity in magnitude up to 10^?2 S/cm at room temperature without external additives.     

Electrochemical polymerization of pyrrole in BMIMPF6 ionic liquid and its electrochemical response to dopamine in the presence of ascorbic acid

Polypyrrole (PPy) film modified glassy carbon (GC) electrode was prepared by electrochemical polymerization in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) room temperature ionic liquid. The PPy film obtained in ionic liquid adhered on the electrode surface well and the properties of the PPy film have been characterized via UV–vis spectra and scanning electron microscopy (SEM). The electrochemical response of the PPy modified electrodes toward ascorbic acid (AA) and dopamine (DA) was investigated by differential pulse voltammetry (DPV). Well separated anodic peaks were observed at PPy electrode with peak separation (ΔE) of 200 mV at pH 6.2. Compared with PPy electrode prepared in aqueous solution, DA has a higher oxidation currents at the modified electrode prepared in ionic liquid. The oxidation peak potentials and currents were affected by the pH valuation and the film thicknesses.     

Conductive wool yarns by continuous vapour phase polymerization of pyrrole

Conducting polypyrrole (PPy) coated wool yarns were prepared by a continuous vapour polymerization technique, using a speed of 1 m/min with different iron(III) chloride (FeCl₃) as the oxidant at different concentrations. The resistivities, tensile properties, longitudinal and cross-sectional views of PPy-coated wool yarns were investigated. Optimum specific electrical resistances of 2.96 Ω g/cm² at 80 g/L FeCl₃ and 1.69 Ω g/cm² at 70 g/L FeCl₃ were obtained for 500 and 400 twist per meter (TPM) yarns, respectively. PPy-coated wool yarns exhibited higher elongation than uncoated yarns. Longitudinal and cross-sectional views of the yarns indicate that PPy coating penetrated deep into the yarn cross-section and a uniform coating was obtained on the surface of the yarn surface.     

Effect of sulphate ion on the electrochemical polymerization of pyrrole and N-methylpyrrole

Pyrrole and N-methylpyrrole were electrochemically polymerized in an identical manner in aqueous electrolytes containing (Et₄N)BF₄, LiClO₄ or Na₂SO₄ to give films of the corresponding p-doped polymers. The polymer obtained from the aqueous Na₂SO₄ electrolyte, [(poly N-methylpyrrole)^+y (SO₄)_y/2^2-]_x, differed from the other polymers in that it exhibited a very low conductivity (≈ 10^?7 S/cm), contained a high concentration of > C=O groups and had an EPR linewidth, ΔH_pp, more than an order of magnitude greater than that found in the corresponding polymers obtained from the (Et₄N)BF₄ and LiClO₄ electrolytes. A sample of [(polyN-methypyrrole)^+y(BF₄)_y^?]_x electrochemically synthesized in CH₃CN and subsequently converted electrochemically to the corresponding sulphate in the Na₂SO₄ aqueous electrolyte exhibited normal behaviour. A mechanism is proposed for the introduction of > C=O groups into the poly(N-methylpyrrole) polymer during its electrochemical polymerization in the Na₂SO₄ aqueous electrolyte.     

An electrically-conductive composite prepared by electrochemical polymerization of pyrrole into polyurethane

A study of the electrochemical preparation of conductive composite films from polypyrrole and non-conducting polyurethane resin is presented. Pyrrole and dopants can penetrate through a polyurethane substrate (precoated on a Pt electrode by casting) and electropolymerize on the Pt surface due to the swelling of the coating by the electrolyte solution (dry acetonitrile mixed with ethylene glycol). Cyclic voltammograms show that the diffusion process in polyurethane is inhibited for larger anions. The electrical conductivity of the composites falls in the range 1–35 S/cm and is influenced by the electropolymerization conditions (electrode potential, reaction time, type of supporting electrolyte, etc.). The mechanical properties of the composites resemble those of pure polyurethane. Scanning electron micrographs, FT infrared spectra and other experiments indicate that polypyrrole is dispersed in the polyurethane matrix like a net with unusually thickset ‘knots’.     

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.     

Synthesis and characterization of triphenylamine derivatives by oxidative polymerization

Hole transport polymers consisting of 4-methoxytriphenylamine (P-MOTPA) and 4-n-butyltriphenylamine (P-BTPA) were synthesized by oxidative coupling reaction using FeCl₃ as an oxidant. These polymers had good solubility and their thin films showed sufficient morphological stability. ¹H NMR and ¹³C NMR revealed that the monomers were exclusively connected at the p-positions of unsubstituted phenyl groups. Polymers had UV absorption maximum around 370 nm. Cyclic voltammograms of polymers showed well-defined pairs of reduction and oxidation peaks at 1.1 V versus Ag/AgCl, indicating that the polymers are electrochemically active. P-MOTPA and P-BTPA had hole drift mobility of being 4.04 × 10⁻⁵ and 2.98 × 10⁻⁵ cm²/V s at the electric field of 50 V/μm, respectively.     

Core-shell attapulgite@polyaniline composite particles via in situ oxidative polymerization

A facile method was developed for the preparation of core-shell attapulgite@polyaniline (ATP@PANI) composite particles via in situ oxidative polymerization after the surface modification of the attapulgite nano-fibrillar clay (ATP) with anilinium chloride salt. The possible encapsulation mechanism was supposed. The composite particles were characterized by FTIR, UV–vis, and TGA. The core-shell morphologies of the composite particles like Chinese date were confirmed by TEM and SEM. The effect of the concentration of hydrochloric acid on the morphologies and the electrical conductivities of the ATP@PANI composite particles was also investigated.     

Synthesis of conductive elastomeric foams by an in situ polymerization of pyrrole using supercritical carbon dioxide and ethanol cosolvents

Electrically conductive polyurethane (PU) foams were prepared by first impregnating a PU foam with ferric trifluoromethane sulfonate (ferric triflate) using supercritical carbon dioxide (scCO₂) containing 0.2–1.3 vol.% ethanol as a cosolvent, and then exposing the foam to pyrrole vapor. Polypyrrole (PPy) was formed in situ by an chemical oxidative polymerization. The conductivity of the composite foams ranged from 10⁻⁷ to 10⁻² S/cm, depending on the amount of ethanol and impregnation time used. The amount of PPy produced depended on the amount of oxidant absorbed by the foam. For low ethanol concentrations and/or short impregnation time, the PPy produced was concentrated at or near the surfaces of the foam sample. The dispersion of the PPy in the foam was improved by increasing the amount of ethanol and the impregnation time. Ferric trifluoroacetate was more soluble in the scCO₂/ethanol solutions, but produced foams with much lower conductivity than did ferric triflate.     

Chemical polymerization of aniline using periodic acid in acetonitrile

The chemical polymerization of aniline in anhydrous medium was investigated using periodic acid, H₅IO₆ as an oxidant. This is the first time that H₅IO₆ has been used as an oxidant in the chemical synthesis of conductive polymers. The product was characterized by FTIR, UV–vis spectroscopies, scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric (TG) analysis, and electrical conductivity measurements. EDX and thermogravimetric analysis showed that Pani includes ClO₄⁻ and iodine or iodide ion as dopants. Electrical conductivity of polyaniline with H₅IO₆ was measured as 100 S cm⁻¹. H₅IO₆ oxidant produces first IO₃⁻ and then I₂. Therefore, it could ensure both oxidation of aniline by IO₃⁻ and then doping polyaniline with I₂, without any residual oxidant contamination. I₂, which is a well known extrinsic dopant, was produced intrinsically in this study. Thus, H₅IO₆ was found to be an effective oxidant material for the chemical polymerization of aniline.     

Polypyrrole/vermiculite nanocomposites via self-assembling and in situ chemical oxidative polymerization

Conductive polypyrrole (PPy) was chemically grafted from the self-assembled monolayer (SAM) coated on expanded vermiculite (VMT), resulting in PPy/VMT nanocomposites after VMT particles were surface modified. X-ray diffraction (XRD) analysis confirmed that the main peaks of PPy/VMT nanocomposites are similar to the SAM–VMT particles, which reveal that the crystal structure of SAM–VMT is well maintained after the coating process under polymerization conditions and exhibit semi-crystalline behavior. Thermogravimetric analysis shows that the thermal stability of PPy/VMT nanocomposites was enhanced and these can be attributed to the retardation effect of amine-functionalized VMT as barriers for the degradation of PPy. The morphology of PPy/VMT nanocomposites showed the sheet structure and encapsulated morphology. The composites possess high electrical conductivity at room temperature, weakly temperature dependence of the conductivity.     

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.     

Intercalation compounds of graphite: Chemical identity and reactivity

Although both the true intercalation compound “C₁₃CrO₃” and the commercially available Seloxcette graphite/chromium trioxide mixture are reduced by various inorganic reagents, only the Seloxcette is efficacious in oxidizing primary alcohols to aldehydes. The nature of this divergence is probed by chemical and physical techniques. Curiously, while both the Seloxcette and the “C₁₃CrO₃” are found to contain chromium in a mixture of oxidation states, just as many intercalation compounds contain metals of different oxidation states, the immobility of the chromium in “C₁₃CrO₃” precludes reaction with organic species. The results found for these chromium systems are generalized to a discussion of the chemical reactivity of other intercalation compounds.     

Core-shell attapulgite@polypyrrole composite with well-defined corn cob-like morphology via self-assembling and in situ oxidative polymerization

Conductive polypyrrole (PPy) layer was chemically grafted from the self-assembled monolayer (SAM) coated on ATP, resulting in SAM-ATP@PPy composites after attapulgite (ATP) particles were surface modified. The composites possess high electrical conductivity at room temperature, weakly temperature dependence of the conductivity. X-ray diffraction (XRD) analysis confirmed that the main peaks of SAM-ATP@PPy composites are similar to the SAM-ATP particles, which reveal that the crystal structure of SAM-ATP is well-maintained after the coating process under polymerization conditions and exhibit semi-crystalline behavior. Thermogravimetric analysis shows that the thermal stability of SAM-ATP@PPy composites was enhanced and these can be attributed to the retardation effect of amine-functionalized ATP as barriers for the degradation of PPy. The morphology of SAM-ATP@PPy composites showed the fibrillar structure and well-defined corn cob-like morphology.