Polypyrrole Content Research Articles

A methacryl ethyl-functionalized soluble polypyrrole: Synthesis, characterization, and potentiality in rapid fabrication of high-aspect-ratio pillar arrays

A methacryl ethyl-functionalized soluble polypyrrole was designed and prepared by chemical oxidative polymerization for rapid fabrication of high-aspect-ratio pillar arrays. The chemical structures of the pyrrole derivative and the corresponding polypyrrole were characterized by FTIR and 1H NMR. The polypyrrole with a weight-average molecular weight (Mw) of 7376 exhibits good solubility in several organic solvents, favorable thin film-forming ability and two UV–Vis absorption peaks at 280 and 380nm in tetrahydrofuran solution. The dilute chloroform solution of the polypyrrole is a Newtonian fluid with a low viscosity and shows a significant increase in the electrical conductivity with increasing the polypyrrole content. Moreover, an insulating photoresist can be transformed into a conductive photoresist by doping this polypyrrole. Electrowetting driven structure formation experiments have confirmed that the conductive photoresist can fulfill rapid fabrication of higher-aspect-ratio pillar arrays compared with the insulating photoresist.

Antimicrobial activity and cytotoxicity of cotton fabric coated with conducting polymers, polyaniline or polypyrrole, and with deposited silver nanoparticles

Cotton fabric was coated with conducting polymers, polyaniline or polypyrrole, in situ during the oxidation of respective monomers. Raman and FTIR spectra proved the complete coating of substrates. Polypyrrole content was 19.3wt.% and that of polyaniline 6.0wt.%. Silver nanoparticles were deposited from silver nitrate solutions of various concentrations by exploiting the reduction ability of conducting polymers. The content of silver was up to 11wt.% on polypyrrole and 4 wt.% on polyaniline. The sheet resistivity of fabrics was determined. The conductivity was reduced after deposition of silver. The chemical cleaning reduced the conductivity by less than one order of magnitude for polypyrrole coating, while for polyaniline the decrease was more pronounced. The good antibacterial activity against S. aureus and E. coli and low cytotoxicity of polypyrrole-coated cotton, both with and without deposited silver nanoparticles, were recorded, and they promise a broad applicability of this material. Polyaniline-coated samples showed lower antibacterial activity and higher cytotoxicity compared to polypyrrole-based materials.

A novel method for synthesis of polypyrrole grafted chitin

In this paper we report the grafting of polypyrrole (PPy) on to a biopolymer, chitin. Polypyrrole is chemically grafted onto chitin by using ammonium peroxydisulphate (APS) initiator, in the presence of 1 M HCl. The effects of concentration of polypyrrole on graft copolymer are studied by determining the grafting percentage. Grafting of polymer is further verified by dissolution studies. Grafted polymer samples are characterized by Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectrum, X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA) and conductivity studies. Mechanism of grafting has been proposed on the basis of experimental results.

Effects of Selective Polymerization Conditions on Physical Properties of Nanometer‐Scale Silica/Polypyrrole Composites

Nanometer‐scale (approximately 70 nm) silica/polypyrrole composites were synthesized using a selective polymerization based on an in situ‐generated strong oxidizing agent (NO + ions) on the silica surface. The effects of the concentrations of reactants (pyrrole monomer and NO2 − ions) and the presence of additional dopant anions (Cl− or ) on the polypyrrole (ppy) content and electric conductivity of the silica/ppy composites are examined. It was found that the ppy content in the silica/ppy composites increased with the reactant concentration in the range of 0.02–0.2 M. It is revealed that employing additional dopant anions could be a promising way to improve the electrical conductivity of the composites.

Synthesis and characterization of Fe3O4/polypyrrole/carbon nanotube composites with tunable microwave absorption properties: Role of carbon nanotube and polypyrrole content

Two different sizes of Fe3O4 nanoparticles were synthesized by hydrothermal (H-Fe3O4, ≈100nm) and co-precipitation (C-Fe3O4, ≈20nm) methods. Further, Fe3O4/polypyrrole (Ppy) composites were prepared by polymerizing the conductive monomer, pyrrole on the surface of Fe3O4. In addition, we also synthesized Fe3O4/Ppy/carbon nanotube (CNT) composites by blending the CNTs with Fe3O4/Ppy composites. Epoxy resin-based microwave absorbers were prepared at different thicknesses (1, 2 and 3mm) by mixing 20% by weight of the as-prepared composites and the complex permittivity (ε′−jε″) and permeability (μ′−jμ″) were measured in the 2–18GHz frequency range. The composites exhibited significant improvement in microwave absorption (reflection loss⩽−10dB) with a bandwidth from 8 to 12.5GHz (X-band) by matching the magnetic properties of Fe3O4 and the dielectric properties of Ppy and CNTs for 20wt% of fillers in 3-mm thickness absorbers. The addition of CNTs into H-Fe3O4/Ppy composites further enhances the minimum reflection loss from −15.8 to −25.9dB. The present results can pave the way to construct microwave absorbers with a desired reflection loss at a target frequency and thus, the efficient complementarities between complex permittivity and permeability of the nanocomposites can be achieved.

Electrical transport in titania nanoparticles embedded in conducting polymer matrix

Abstract Conducting polymer-wide band gap semiconductor nanocomposites are prepared by polymerizing pyrrole in the presence of colloidal titanium dioxide (TiO2) sol. Characterizations of nanocomposites are carried out by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Direct current (dc) and alternating current (ac) conductivities of nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polypyrrole (PPY). The temperature dependence of ac conductivity suggests that small polaron tunneling occurs in the charge transfer process. A very large dielectric constant of about 13,000 at room temperature has been observed. The interface between PPY and TiO2 plays an important role in yielding a large dielectric constant in the composite.

Frequency and Temperature Dependence of Dielectric Behaviors for Conductive Acrylic Composites

ABSTRACTIn this study, acrylic‐based conductive polymeric composite thin films were prepared by in situ chemical polymerization of pyrrole (Py) in the case of ammonium persulfate (APS) and iron(III) chloride (FeCl3). Composite thin films were produced by the solution casting method. The effect of polypyrrole (PPy) content and the type of oxidant on the morphological and dielectric properties were investigated. Temperature‐ and frequency‐dependent dielectric properties were also studied in a frequency domain starting from 0.01 Hz to 10 MHz and in a temperature domain from 35 to 195°C. The results revealed that the dielectric constant and dielectric loss increased, whereas temperature and the highest dielectric values were obtained in the case of APS. The density of interconnected pores enwrapped with PPy under the surface improved the electrical/dielectric properties of the composite thin films.

Preparation and electrical properties of polypyrrole containing photocured thiol–ene based composites

Abstract In this study, UV curable polypyrrole containing thiol–ene based composite films were prepared by the reaction between Propoxylated (2) neopentyl glycol diacrylate (SR 9003), Trimethylolpropane tris(3-mercaptopropionate), (3-mercaptopropyl)trimethoxysilane, 1-vinyl-2-pyrrolidinone and polypyrrole. FT-IR was used to confirm the formation of the composites. Thermal stability of the samples was evaluated by thermogravimetric analysis (TGA). The samples were characterized with the following analysis; gel content, water absorption capacity. Hydrophobicity of the samples was determined by the contact angle measurements. Direct current (dc) conductivity measurements of samples were performed depending on polypyrrole content in the composites at room temperature. Capacitance measurements (40 Hz–100 kHz) of the samples were performed in the temperature range of 295–378 K. Dc conductivity and capacitance values of the samples were measured in vacuum in dark. Dc conductivity measurements revealed that dc conductivity values increased with increasing polypyrrole content. Dielectric measurements revealed that dielectric constant of the samples increased with increasing temperature and decreased with increasing frequency. It is also observed that dielectric constant of the samples decreased with increasing polypyrrole content.

Novel germanium/polypyrrole composite for high power lithium-ion batteries.

Nano-Germanium/polypyrrole composite has been synthesized by chemical reduction method in aqueous solution. The Ge nanoparticles were directly coated on the surface of the polypyrrole. The morphology and structural properties of samples were determined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis was carried out to determine the polypyrrole content. The electrochemical properties of the samples have been investigated and their suitability as anode materials for the lithium-ion battery was examined. The discharge capacity of the Ge nanoparticles calculated in the Ge-polypyrrole composite is 1014 mAh g−1 after 50 cycles at 0.2 C rate, which is much higher than that of pristine germanium (439 mAh g−1). The composite also demonstrates high specific discharge capacities at different current rates (1318, 1032, 661, and 460 mAh g−1 at 0.5, 1.0, 2.0, and 4.0 C, respectively). The superior electrochemical performance of Ge-polypyrrole composite could be attributed to the polypyrrole core, which provides an efficient transport pathway for electrons. SEM images of the electrodes have demonstrated that polypyrrole can also act as a conductive binder and alleviate the pulverization of electrode caused by the huge volume changes of the nanosized germanium particles during Li+ intercalation/de-intercalation.

Polypyrrole‐contained electrospun conductive nanofibrous membranes for cardiac tissue engineering

Cardiac tissue engineering (TE) is one of the most promising strategies to reconstruct infarct myocardium and the major challenge is to generate a bioactive substrate with suitable chemical, biological, and conductive properties, thus mimicking the extracellular matrix (ECM) both structurally and functionally. In this study, polypyrrole/poly(ε-caprolactone)/gelatin nanofibrous scaffolds were electrospun by incorporating different concentrations of polypyrrole (PPy) to PCL/gelatin (PG) solution. Morphological, chemical, mechanical, and biodegradation properties of the electrospun nanofibers were evaluated. Our data indicated that by increasing the concentration of PPy (0-30%) in the composite, the average fiber diameters reduced from 239 ± 37 nm to 191 ± 45 nm, and the tensile modulus increased from 7.9 ± 1.6 MPa to 50.3 ± 3.3 MPa. Conductive nanofibers containing 15% PPy (PPG15) exhibited the most balanced properties of conductivity, mechanical properties, and biodegradability, matching the requirements for regeneration of cardiac tissue. The cell proliferation assay, SEM, and immunostaining analysis showed that the PPG15 scaffold promote cell attachment, proliferation, interaction, and expression of cardiac-specific proteins better than PPG30. Electrospun PPG15 conductive nanofibrous scaffold could be desirable and promising substrates suitable for the regeneration of infarct myocardium and cardiac defects.

Advanced NOx gas sensing based on novel hybrid organic–inorganic semiconducting nanomaterial formed between pyrrole and Dawson type polyoxoanion [P2Mo18O62]6−

Dawson-type K6P2Mo18O62·nH2O can be used as an oxidizing agent to polymerize pyrrole and yield a hybrid organic–inorganic nanostructured material [{Py}6(P2Mo18O62)]x. By adding the mild reducing agent potassium iodide (KI), the polymerization process was controlled to generate a hybrid material with low polypyrrole content [K4{Py}2(P2Mo18O62)]y. The electrical transport properties of [K4{Py}2(P2Mo18O62)]y displayed a perfect transistor operation suitable for gas sensing applications. Exposure of [K4{Py}2(P2Mo18O62)]y to various gases illustrated a selective and sensitive response to NOx gases. In addition, an interesting extended linearity up to 5500 ppm was recorded.

Influences of carbon support on the electrocatalysis of polypyrrole-modified cobalt hydroxide in the direct borohydride fuel cell

Catalysts of Co(OH) 2 supported on polypyrrole-modified Super P carbon and on polypyrrole-modified BP 2000 carbon are prepared by a chemical method. The structure and morphology of the catalysts are characterized by X-ray diffraction, X-ray photoemission spectroscopy and transmission electron microscopy. BP 2000 carbon demonstrates larger specific surface area, lower crystallization degree and lower electrochemical resistance than Super P carbon. The surface characteristics of the carbon support have notable influences on the morphology and electrocatalytic activity of Co(OH) 2. Co(OH) 2 distributes much homogeneously on the polypyrrole-modified BP 2000 with more polypyrrole content, and exhibits higher electrocatalytic activity compared with that on polypyrrole-modified Super P carbon. The DBFC using Co(OH) 2 supported on polypyrrole-modified BP 2000 as the catalysts demonstrates fairly good performance (160 mW cm −2) under ambient conditions.

Fabrication of carbon nanofiber-driven electrodes from electrospun polyacrylonitrile/polypyrrole bicomponents for high-performance rechargeable lithium-ion batteries

Carbon nanofibers were prepared through electrospinning a blend solution of polyacrylonitrile and polypyrrole, followed by carbonization at 700 °C. Structural features of electrospun polyacrylonitrile/polypyrrole bicomponent nanofibers and their corresponding carbon nanofibers were characterized using scanning electron microscopy, differential scanning calorimeter, thermo-gravimetric analysis, wide-angle X-ray diffraction, and Raman spectroscopy. It was found that intermolecular interactions are formed between two different polymers, which influence the thermal properties of electrospun bicomponent nanofibers. In addition, with the increase of polypyrrole concentration, the resultant carbon nanofibers exhibit increasing disordered structure. These carbon nanofibers were used as anodes for rechargeable lithium-ion batteries without adding any polymer binder or conductive material and they display high reversible capacity, improved cycle performance, relatively good rate capability, and clear fibrous morphology even after 50 charge/discharge cycles. The improved electrochemical performance of these carbon nanofibers can be attributed to their unusual surface properties and unique structural features, which amplify both surface area and extensive intermingling between electrode and electrolyte phases over small length scales, thereby leading to fast kinetics and short pathways for both Li ions and electrons.

The effect of polypyrrole on arteriogenesis in an acute rat infarct model

The conductive polymer polypyrrole was blended with alginate to investigate its potential in tissue engineering applications. This study showed that increasing the polypyrrole content altered the macroscopic structural morphology of the polymer blend scaffold, but did not alter the overall conductivity of the polymer blend, which was 10 −2 S/cm 2. Culturing of human umbilical vein endothelial cells on the polymer blend scaffolds showed that addition of polypyrrole mediated cell attachment to the polymer scaffold. However, cell proliferation was dependent on the polypyrrole content with 0.025% v/v polypyrrole giving the best results. Using an ischemia–reperfusion rat myocardial infarction model, local injection of 0.025% polypyrrole in alginate polymer blend into the infarct zone yielded significantly higher levels of arteriogenesis at 5 weeks post-treatment when compared with the saline control group and the alginate only treatment group. In addition, this alginate–polypyrrole polymer blend significantly enhanced infiltration of myofibroblasts into the infarct area when compared with the control group. The results of this study highlight the potential clinical benefit of using this alginate–polypyrrole polymer blend as an injectable scaffold to repair ischemic myocardium after myocardial infarction.

Optical and diode like current–voltage characteristics of SnO2–polypyrrole nanocomposites

Nanocomposites based on conducting polypyrrole (PPY) and inorganic SnO2 have been synthesized by the soft chemical route. Absorption spectra of PPY–SnO2 nanocomposites show peaks at wavelengths of 310–340 nm corresponding to nanosized SnO2 and two broad bands present at around 450–475 nm and in the range 600–900 nm are due to polypyrrole. The absorption band at lower wavelength indicates a blue shift of about 30 nm with respect to bulk SnO2. Direct current conductivity of nanocomposites as a function of temperature for different concentrations of polypyrrole have been interpreted by three-dimensional Mott's variable range hopping process. The observed diode like current–voltage characteristics are satisfactorily explained using the Schottky type barriers.

Electrochemically deposited polypyrrole films and their characterization

Ionically conductive polypyrrole films have been deposited at 295 K from anhydrous acetonitrile, acetonitrile/H 2O and NaBF 4 aqueous solutions onto platinum, mild steel and stainless steel discs, using cyclic voltammetry, potentiostatic and galvanostatic techniques. Cyclic voltammetry of the polymer films has been studied as a function of water content of the acetonitrile solvent, polypyrrole concentration and potential sweep rate. Potentiostatic growth of thicker (< 30 micron) films on stainless steel allowed free-standing polypyrrole membranes to be produced. Well adherent and conductive films were deposited at constant potential in stirred solutions from acetonitrile electrolytes containing 1% (v/v) of water. The membrane resistivity of the reduced films in 0.5 mol dm − 3 KCl (aq) at 295 K was ≈ 1 × 10 6 Ω cm, while the resistivity of the oxidised membrane was 2700 Ω cm.

Electrical conductivity and dielectric properties of SiO2 nanoparticles dispersed in conducting polymer matrix

Electrical and dielectric properties of conducting polypyrrole–wide band gap silica (PPY–SiO2) nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polypyrrole. The average grain size of the nanocomposites is in the range of 40–80 nm. Impedance spectra reveal two distorted semicircles corresponding to grain and grain boundary effects. The magnitude of conductivity and its temperature variation are significantly different from polypyrrole and silica. A very large dielectric constant of about 4800 at 30 kHz and at room temperature has been observed for the highest concentration of silica. Inhomogeneous behavior of nanocomposites gives rise to high dielectric constant.

Magnetic properties of polypyrrole-coated iron oxide nanoparticles

Iron oxide nanoparticles were prepared using the sol–gel process. In situ polymerization of a pyrrole monomer in the presence of oxygen in an iron oxide–ethanol suspension resulted in an iron oxide polypyrrole nanocomposite. The structure and magnetic properties of the nanocomposites with varying pyrrole concentrations are investigated. X-ray diffraction studies indicate the presence of the γ-Fe2O3 phase for the concentrations investigated. FTIR studies confirm the presence of polypyrrole. TEM studies show agglomeration in uncoated samples and in samples with a lower concentration of polypyrrole. Agglomeration is greatly reduced for samples coated with a higher concentration of polypyrrole. The ac susceptibility measurements performed in the temperature range 77–300 K show the presence of blocking, indicating the superparamagnetic phase. The blocking temperature is found to depend on the pyrrole concentration. Monte Carlo studies for an array of polydispersed single domain magnetic particles, based on an interacting random anisotropy model, were also carried out, and the blocking temperatures obtained from the simulation of the field cooled–zero field cooled magnetization compare favourably with experimental results.

Towards High Power Polypyrrole/Carbon Capacitors

Conducting polymers demonstrate effective capacitances of more than 100 Farads per gram, 5 orders of magnitude higher than traditional capacitors. However polymer discharge times tend to be on the order of seconds, as opposed to the milli or microseconds of conventional capacitors, so that the overall power density is still at least an order of magnitude lower. The polypyrrole devices are essentially electrolytic capacitors in which charging times appear to be limited by rates of ionic mass transport and RC charging times. Electrochemical impedance measurements suggest diffusion time constants of 33 ms in 158 nm thick polypyrrole films with volumetric capacitances of 10 7 F/m 3. The impedance of a highly porous polypyrrole/carbon composite was measured to investigate the achievement of similarly fast response times in much thicker materials. It is shown that increasing the polypyrrole content of the film increases capacitance up to 60 F/g, but also increases the charging time constant. Analysis of the rate limiting factors suggests a method of optimizing capacitor geometry in order to maximize rates, including the prediction of device geometries that will lead to power delivery matching those of traditional capacitors.

Polypyrrole-coated styrene-butyl acrylate copolymer composite particles with tunable conductivity

A series of near or monodisperse styrene-butyl acrylate (SBA) copolymer latex particles with different butyl acrylate contents were coated with polypyrrole. The structure of the SBA/PPy composites was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and standard four-probe method. The core-shell morphology of the SBA/PPy composite particles was confirmed. The result of DSC showed that Tg of the composite is mainly determined by the core component. The effects of the concentration of polypyrrole, the butyl acrylate content in SBA copolymer and the nature of the counter-anion on the electrical conductivity of compression-moulded samples were studied. It was first found that the electrical conductivity of the samples can be tuned by varying the butyl acrylate content in SBA copolymer and the highest conductivity of the core-shell composite was 0.17 S · cm−1.