Polypyrrole Composites Research Articles

Synthesis and characterization of hexagonal ferrite Co2Sr2Fe12O22 with doped polypyrrole composites

Y-type hexagonal ferrite Co2Sr2Fe12O22 was prepared by microemulsion route. A conducting polymer, polypyrrole was chemically synthesized and doped with dodecylbenzenesulphonic acid (PPy·DBSA). FTIR and magnetic properties of Co2Sr2Fe12O22 were investigated and compared with composite made by mixing the Co2Sr2Fe12O22 with this conducting polymer PPy–DBSA by 1:1 molar ratio. Phase analysis was performed by using X-ray diffraction (XRD). The microstructure was examined by scanning electron microscopy (SEM) showing heterogonous distribution of grains. The field dependent magnetic properties of the prepared samples were investigated at room temperature by using vibrating sample magnetometer (VSM). It has been observed that mixing of polymer in ferrite plays a crucial role in enhancing the coercivity, while saturation magnetization (Ms) and remanance were observed to decrease. Due to fine grain size, the density of grain boundaries increases where the domain wall pinning can take place, hence the coercivity of the composite samples increases. Appreciable improved value of coercivity guaranteed the use of these synthesized materials in the recording media, which is =1896(Oe) in the present samples. The suitable signal-to-noise ratio in the high density recording media can be achieved due to small particles size of this synthesized composite, which is expected in the present ferrite–polymer composite sample.

Carbon-fiber composites of organometallic intercalated polyaniline and polypyrrole doped with sodium polystyrene sulfonate as electrodes for lithium-ion batteries

Carbon fiber (CF) composites of organometallic intercalated polyaniline (Pani) and polypyrrole (Ppy) doped with polystyrene sulfonate (PSS) were electrochemically synthesized and tested as electrodes for lithium-ion batteries. From the results obtained by cyclic voltammetry, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy, it was concluded that the incorporation of copper(II) ions in the polymeric composite was successfully attained by adsorption of Cu2+ ions and 2,5-dimercapto-1,3,4-thiadiazole (DMcT) monomers on the carbon microfibers. The experimental electrochemical impedance response of the obtained Pani(DMcT–Cu ion)/CF composite was simulated by adequate equivalent electrical circuits. After 20 charge/discharge cycles, the experimental discharge specific capacity of the Pani(DMcT–Cu ion)/CF composite was 118 mA h g−1 (100% coulombic efficiency) using a 1 mol L−1 LiClO4 solution in propylene carbonate, and 110 mA h g−1 when a polymeric electrolyte was used. In the charge/discharge tests of the Ppy-PSS/Pani/CF composite as anode, a high discharge specific capacity of 225 mA h g−1 was obtained after 20 cycles. The resulting Ppy-PSS/Pani/CF/polymeric electrolyte/Pani(DMcT–Cu ion)/CF battery presented a specific capacity of 62 mA h g−1 and could be charged up to 2.0 V, yielding an energy density 425 W h g−1, with a coulombic efficiency of about 98%.

In Situ Synthesis of Graphene/Amine-Modified Graphene, Polypyrrole Composites in Presence of SrTiO3 for Supercapacitor Applications

Composites based on both unmodified and amine-modified graphene were successfully prepared via in situ oxidative polymerization of pyrrole in presence of SrTiO3. To characterize the graphene/amine-modified graphene-polypyrrole-SrTiO3 composite electrodes, cyclic voltammetry test for measuring specific capacitance, cyclic charge discharge test and an ac impedance test were executed. The composite with unmodified graphene showed better specific capacitance but a little lower cyclability compared to that of modified graphene composite. The presence of SrTiO3 ensures the better thermal stability of the composites compared to that of simple graphene–polypyrrole composite.

Flexible and high surface area composites of carbon fiber, polypyrrole, and poly(DMcT) for supercapacitor electrodes

Thin films of polypyrrole (Ppy) and poly-2,5-dimercapto-1,3,4-thiadiazole (poly(DMcT)) are electrochemically deposited on pieces of carbon fiber (CF) cloth, yielding flexible and high surface area composites that are characterized as electrodes for supercapacitors. A bilayered polymeric composite (CF/poly(DMcT)/Ppy) is obtained by depositing a nanometric layer of Ppy on CF already supporting a poly(DMcT) film. Electrochemical stability tests indicate that the Ppy film acts as a barrier that prevents the loss of the poly(DMcT) electroactive material, thus improving the charge-storage characteristics of the bilayered film even after 1000 cycles. Specific capacitance values of 460±50 and 1130±100Fg−1 are observed for electrodes made of the CF/Ppy and CF/poly(DMcT)/Ppy composites, respectively. Comparatively to similar Ppy composite materials used for supercapacitors, the bilayered film electrode here reported presents a significantly improved specific capacitance value.

Enhancing the Interface in Silk–Polypyrrole Composites through Chemical Modification of Silk Fibroin

To produce conductive, biocompatible, and mechanically robust materials for use in bioelectrical applications, we have developed a new strategy to selectively incorporate poly(pyrrole) (Ppy) into constructs made from silk fibroin. Here, we demonstrate that covalent attachment of negatively charged, hydrophilic sulfonic acid groups to the silk protein can selectively promote pyrrole absorption and polymerization within the modified films to form a conductive, interpenetrating network of Ppy and silk that is incapable of delamination. To further increase the conductivity and long-term stability of the Ppy network, a variety of small molecule sulfonic acid dopants were utilized and the properties of these silk-conducting polymer composites were monitored over time. The composites were evaluated using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), optical microscopy, energy-dispersive X-ray (EDX) spectroscopy, cyclic voltammetry, a 4-point resistivity probe and mechanical testing. In addition, the performance was evaluated following exposure to several biologically relevant enzymes. Using this strategy, we were able to produce mechanically robust polymer electrodes with stable electrochemical performance and sheet resistivities on the order of 1 × 10(2) Ω/sq (conductivity ∼1 S/cm).

Electrochemical Synthesis and Characterization of Multi-walled Carbon Nanotubes/Polypyrrole and Polypyrrole Hollow Nanotubes

We report the electrochemical synthesis and characterization of hybrid structures composed by hollow nanotubes of polypyrrole and core-shell composites of multi-walled carbon nanotubes (MWCNTs) coated by polypyrrole (PPy). The synthesis of these systems is critically dependent on relative concentration of carbon nanotubes (introduced as a template for polymerization) and affects the level of conductivity of media, the diameter and relative roughness of synthesized nanotubes. The competition induced by polymerization on the surface of different templates (aggregates of methyl orange and MWCNT) allows that smooth structures can be obtained, minimizing the synthesis of granules of polypyrrole, in a process that affects the morphology, thermal and electrical properties of synthesized materials. As a result, the impedance of mixed composite is lower than the other obtained for each system (MWCNT and hollow nanotubes of PPy), in an indication that synergistic interaction is favored during the synthesis.

Two formation mechanisms and renewable antioxidant properties of suspensible chitosan–PPy and chitosan–PPy–BTDA composites

Treatment of chitosan together with pyrrole (Py) by oxidant sodium nitrite (NaNO2) forms unique chitosan–polypyrrole composites suspensible in diluted acetic acid. It was discovered that the reactive species polymerizing Py into polypyrrole (PPy) are the aldehydes, formed in situ during the depolymerization reaction of chitosan with NaNO2. In situ UV–vis and FTIR measurements identify typical porphyrin signals, shedding light to the formation mechanism. To improve the film formation of the composites, the application of additional cross-linking agents such as 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) was investigated. The obtained suspensible chitosan–PPy–BTDA composites showed renewable (by electrochemical means) antioxidant properties comparable in strength to those of natural vitamins.

Enhanced Biotransformation of Dinitrotoluene by Mediator-Functionalized Polypyrrole Composites

The continuous dosing and discharge of water soluble redox mediators such as biologically recalcitrant compounds will result in the secondary contamination. The immobilized redox mediator prepared by incorporation of anthraquinonedisulphon-ate (AQDS) during the electropolymerization of pyrrole monomer on active carbon felt (ACF), AQDS/PPy/ACF, was used for catalyzing bioreduction of 2,4-dinitrotoluene(2,4-DNT) in this study. The results showed that the morphology of the PPy films deposits on ACF are characterized by some globular structure; AQDS/PPy/ACF exhibited good catalytic activity and stability for 2,4-DNT, the enhanced reduction rates obtained in the incubations with AQDS/PPy/ACF was about 5 times that without AQDS/PPy/ACF, the corresponding first-order reduction rate constant k reached 0.045 h-1; 2,4-DNT was reduced to be 2,4-diaminotoluene via 2-amino-4-nitrotoluene and 4-amino-2-nitrotoluene in the system.

Polypyrrole/Poly(acrylonitrile-co-butyl acrylate) Composite

Poly(acrylonitrile-co-butyl acrylate) [P(AN-co-BuA)] was synthesized from acrylonitrile (AN) 95% and butyl acrylate (BuA) 5%—molar ratios—by free-radical polymerization in aqueous media, using ceric ammonium nitrate as an initiator. Pyrrole was oxidatively polymerized in dimethylformamide in the presence of P(AN-co-BuA) matrix to produce polypyrrole (PPy) composites. Composite thin films were produced by solution casting onto smooth glass surfaces. Scanning electron microscopy and Fourier transform infrared–attenuated total reflectance analysis of thin films revealed the presence of PPy in the composite structure. Electrical impedance measurements were conducted to reveal the electrical conductivity change due to increasing PPy content. Enhancing the flexibility of PPy structures, as a composite film composed of PPy, could find substantial utility in the application of PPy products. BuA in a copolymer structure with AN improved the mechanical properties of the resulting copolymer by compensating the mechanical disadvantages of PPy. The butylacrylate containing matrix provided better electrical conductivity and stability than polyacrylonitrile, and the presence of butylacrylate enhanced the electrostatic interaction with PPy. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E784–E792, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21321

Electrodeposition of polypyrrole–carbon nanotube composites for electrochemical supercapacitors

In this work we introduce a new electrochemical strategy for the fabrication of composite polypyrrole (PPY)–multiwalled carbon nanotube (MWCNT) composites for electrochemical supercapacitors (ES). The problem of low adhesion of PPY films on stainless steel and Ni substrates is addressed by the use of pyrocatechol violet (PV) dye as an anionic dopant. The experimental data indicates that strong adhesion of PPY films is attributed to catecholate type of PV bonding. We also find that PV strongly adsorbs on MWCNT and allows efficient dispersion, charging and controlled electrophoretic deposition (EPD) of MWCNT. The use of PV for electropolymerization of PPY and EPD of MWCNT allows the formation of composite films by combined electrodeposition method. Results show that Ni-plaque current collectors developed for high power battery applications can be electrochemically impregnated with PPY–MWCNT to form electrodes for ES. Ni plaque based electrodes offer advantages of significantly higher materials loading and superior capacitive behavior compared to thin film electrodes formed on stainless steel current collectors. The electrodes obtained by pulse impregnation show higher specific capacitance compared to the electrodes prepared by galvanostatic impregnation.

Magnetic titania-silica composite–Polypyrrole core–shell spheres and their high sensitivity toward hydrogen peroxide as electrochemical sensor

A novel core–shell sphere with controlled shell thickness was synthesized by in situ chemical oxidative polymerization of pyrrole on FTS (Fe2O3/TiO2/SiO2 composite) surface. The dual porosity of 2–3nm and 40–50nm in FTS core particle provides the hybrids with a high surface area to volume ratio, which enormously facilitates the molecule diffusion process. Furthermore, the porous FTS particle encapsulate Fe2O3 and TiO2 leading to its synergetic interaction with the PPy coating based on FTIR analysis. The unique structure and composition of the hybrid spheres result in new sensing property that is not available from their single counterparts. Cyclic voltammetry results demonstrate that the spheres with appropriate concentration of PPy exhibit enhanced electrocatalytic activity toward the reduction of H2O2 in 0.1M phosphate buffer solution. The sensing performance tests show that the hybrids possess good linear response in wide H2O2 concentration range (10–4000μM) and high sensitivity to H2O2 (0.653AM−1cm−2) at room temperature. The formation mechanism of the spheres was proposed based on the fact that the FTS core was coated firstly by a smooth PPy layer and then PPy nanoparticles. The work reported here provides an alternative concept for preparation of functional materials with new nanostructures and properties.

Benign enzymatic synthesis of multiwalled carbon nanotube composites uniformly coated with polypyrrole for supercapacitors

AbstractBACKGROUND: Recently, various composites of carbon nanomaterials and conducting polymers have been actively investigated as potential electrode materials for supercapacitors which can store and deliver large amounts of electrical energy promptly. Harsh chemical or complex electrodeposition methods have been studied to prepare such composites. In this report, the mild and simple enzymatic catalysis of horseradish peroxidase (EC 1.11.1.7) in aqueous solutions (pH 4.0) was utilized for the first time to prepare composites of multiwalled carbon nanotubes and polypyrrole.RESULTS: Electron micrographs show that in situ enzymatic reaction by horseradish peroxidase enables the uniform coating of multiwalled carbon nanotubes with polypyrrole without containing the polymer aggregates. The specific capacitance of the composites (46.2 F g−1) measured with a two‐electrode cell containing an electrolyte of 1 mol L−1 NaNO3 increased more than four‐fold compared with that obtained with bare multiwalled carbon nanotubes (10.8 F g−1).CONCLUSIONS: Horseradish peroxidase‐catalyzed in situ synthesis of the composites of multiwalled carbon nanotubes and polypyrrole requires neither the derivatization of multiwalled carbon nanotubes and/or pyrrole monomers nor the post‐doping of the synthesized composites to enhance the capacitance of the composites. © 2012 Society of Chemical Industry

Enhanced electrical conductivity of polypyrrole/polypyrrole coated short nylon fiber/natural rubber composites prepared by in situ polymerization in latex

In this paper we report the characterization and properties of conductive elastomeric composites of polypyrrole (PPy) and PPy coated short Nylon-6 fiber (F-PPy) based on natural rubber (NR) prepared by in situ polymerization method. PPy/NR blends were prepared by polymerizing pyrrole in NR latex using anhydrous ferric chloride as oxidizing agent, p-toluene sulphonic acid as dopant and vulcastab VL as stabilizer. PPy/F-PPy/NR composites were prepared as above in presence of short nylon fiber. The products were coagulated out, dried, compounded on a two roll mill and moulded. The cure pattern, DC electrical conductivity, morphology, mechanical properties, thermal degradation parameters and microwave characteristics of the resulting composites were studied. Incorporation of PPy to elastomer retards the cure reaction whereas addition of fiber accelerates the cure reaction. DC conductivity up to 6.25×10−2 was attained for NR/PPy/F-PPy system. The composites containing F-PPy exhibited better mechanical properties compared to NR/PPy systems. The absolute value of the dielectric permittivity, AC conductivity and absorption coefficient of the conducting composites prepared were found to be much greater than the gum vulcanizate. PPy and F-PPy were found to decrease the dielectric heating coefficient and skin depth significantly.

Polypyrrole/MnO2 composites and their enhanced electrochemical capacitance

AbstractThe composites of polypyrrole (PPY) and MnO2 have been prepared through chemical oxidation of pyrrole monomer and MnO2 suspension with ammonium peroxysulfate at low temperature. The morphology and structure of materials were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Transmission electron microscopy (TEM), thermal gravity analysis ‐ differential thermal gravity (TG‐DTG), and X‐ray diffraction (XRD) measurements. The electrochemical properties of the composite were investigated by galvanostatic charge–discharge and electrochemical impedance spectroscopy. The specific capacitance of the composite electrode is 352.8 F/g at a current of 8 mA/cm2 in Na2SO4 electrolyte of 0.5 mol/L, which is much higher than that of 246.2 F/g and 103.5 F/g of PPY and MnO2, respectively. A convenient and effective technique has been developed to fabricate composite materials of PPY and MnO2 promising for designing new capacitors. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and characterization of nanoflake composite multi core-shell SrFe12O19/Fe3O4/PEG/PPy

Nanoflake composite multi core–shell SrFe12O19/Fe3O4/PEG/Polypyrrole was synthesized by in situ polymerization method. In this paper, the fabrication of SrFe12O19 nanoflake is as first core by solgel method. Then fabricated a shell layer from magnetic nanoparticles of Fe3O4, which synthesized by coprecipitation technique, onto the SrFe12O19 nanoflake. Polyethylene glycol (PEG) as a polymer layer and as second shell was coated onto the before core-shell. Than core–shell SrFe12O19/Fe3O4/PEG was used as template for the preparation of SrFe12O19/Fe3O4/PEG/Polypyrrole composite. Final composite has a conductive property among 4.23

Ascorbate electro-oxidation by modified electrodes: Polypyrrole and polypyrrole/Ni(OH)2 composite thin films

The present paper describes the utilization of polypyrrole and the composite of polypyrrole doped with nickel hydroxide modified electrodes toward the catalytic oxidation of ascorbate. Films were potentiostatically deposited onto a glassy carbon surface and Fluor-doped tin oxide glass for different times. The physical characterization was performed using the low angle X-ray diffraction technique. Furthermore, the films were electrochemically characterized using cyclic voltammetry. The X-ray diffraction results show the existence of different polymorphic phases of nickel hydroxide in the polymer matrix, and the β-Ni(OH)2 phase appears to be dominant. The cyclic voltammetry profile in KOH solution shows the presence of two redox peaks that are related to the NiII/NiIII and NiIII/NiII couples, at approximately 0.5 and 0.35V, respectively. The reversible electro-oxidation of ascorbate was observed on the surface of the polypyrrole and composite films. The analytical curves obtained using voltammetric techniques show a linear relationship between the faradaic current and the increase of the ascorbic acid concentration. The sensitivity of these films, which is obtained from the slope of the analytical curves, shows that the composite film is more electroactive than the polypyrrole film: 133.4mALmol−1cm−2 and 83.8mALmol−1cm−2, respectively. The rate constants of the catalytic ascorbate electro-oxidation were also reported, where the mean values were found to be 217.74M−1s−1 and 54.37M−1s−1, for the composite and polypyrrole films, respectively. The low cost of polypyrrole doped with Ni(OH)2 composite electrodes presents a more selective and high sensitivity to determine ascorbic acid concentration.

In vitro and in vivo toxicity of rinsed and aged nanocellulose–polypyrrole composites

Novel composites of nanocellulose and the conducting polymer polypyrrole (PPy) are herein suggested as potential candidates for active ion-extraction membranes in electrochemically controlled hemodialysis. This study has defined processing parameters to obtain a biocompatible nanocellulose-PPy composite, and for the first time, the effect of the composite aging on cell viability has been studied. The influence of rinsing and extraction process steps, as well as aging under different conditions (i.e. in air, at -20°C and in argon), on the electroactivity and cytotoxicity of a PPy-nanocellulose composite has been investigated. The biocompatibility evaluation was based on indirect toxicity assays with fibroblasts and monocyte cell lines and an acute toxicity test in mice, while the electroactivity was evaluated by cyclic voltammetry experiments. The as-prepared composite did not induce any cytotoxic response in vitro or in vivo. Extensive rinsing and 48 h incubation in biological buffer previous to the preparation of the culture medium extracts were, however, necessary to obtain a noncytotoxic composite. The as-prepared composite was also found to exhibit acceptable electrochemical performance, which was retained upon 4 weeks storage in argon atmosphere. It was shown that aging of the composite had a negative effect on biocompatibility, regardless of the storage condition. Thus, to allow for longtime storage of electroactive nanocellulose-PPy hemodialysis membranes, the degradation of PPy upon storage must be controlled. The present results show that the biocompatibility of PPy composites depends on the rinsing and pretreatment of the composite material as well as the aging of the material.

Transition Metal Salt Doping on Polypyrrole/MWCNT Composites for Supercapacitor Applications

AbstractPolypyrrole doped by Zn2+ ions was synthesized as nanocomposites with MWCNT by in‐situ oxidative polymerization and investigated as electrode material for supercapacitors. The uniform coating of polypyrrole on MWCNT was characterized by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effect of Zn2+ ions were characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical performances were investigated by cyclic voltammetry (CV), constant current charging/discharging cyclic test (CC) and electrochemical impedance spectroscopy (EIS) using a three‐electrode system. The doped polypyrrole composites show higher specific capacitance and better cyclic stability.

Effect of polypyrrole on improving electrochemical performance of silicon based anode materials

► Si/PPy composites for lithium ion battery have been synthesized. ► PPy of two microstructures acting as matrix have been synthesized and characterized. ► Two kinds of PPy show different effects on improving electrochemical performance. ► Si/nano-wires PPy shows an improved electrochemical performance. Silicon and polypyrrole composites with different microstructures of polypyrrole were synthesized using high-energy mechanical milling. The nano-wires polypyrrole and micro-particles polypyrrole act as a matrix to hold the active silicon grains as they repeatedly alloy with lithium during the operation of a lithium ion battery. The composite containing 10 wt.% polypyrrole nano-wires exhibits a relative better reversibility and cycle life than bare silicon, while the silicon/micro-particles polypyrrole composite shows no improvement.

Evaluation of the interface aging process of polypyrrole–polysaccharide electrodes in a simulated physiological fluid

Composite polypyrrole–polysaccharide (PPyPSacc) films, such as polypyrrole–heparin (PPyHep), polypyrrole–chondroitin sulfate A (PPyCS-A) and polypyrrole–hyaluronic acid (PPyHA) have been successfully obtained by optimized electrochemical syntheses. The PPyPSacc samples show dopant-mediated tunable physical properties and good stability in air and in biological fluids. The immobilization of PSacc within the polymer matrix renders the surface samples suitable for cell/substrate communication studies. In order to check the viability of PPyPSacc thin films as electrodes for cell electrostimulation, we studied their interface evolution upon aging in a simulated physiological solution (pH=7.4, 37°C) by using electrochemical impedance spectroscopy, cyclic voltammetry and scanning electron microscopy. At open circuit conditions, the overall impedance of the electrodes increases upon aging as a consequence of a fast accumulation of ions at the interface, also related to the increase of porosity and wettability. As the interface impedance increases, the ionic and electronic transport into the polymer is hindered. Nevertheless, no mechanical degradation of the PPyPSacc samples is observed on aging. After 10 days of aging the PPyHep samples keep about 60% of their initial redox capacity. As a consequence the studied materials are capable to supply electrical stimulations to cells in a biological environment well beyond the conventional time-range.