Preparation of conductive,flexible and transparent films by in situ deposition of polypyrrole nanoparticles on polyethylene terephthalate

In this study polypyrrole (PPy) nanoparticles were deposited as a thin film on the modified surface of polyethyleneterephthalate (PET) by in situ chemical polymerization in the presence of sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (DBSNa) and mixture of them as the surfactant. The surface of PET was modified by KOH before deposition and was investigated for conductivity and adhesion of PPy nanoparticles to PET. Resulting conductive flexible films were characterized by UV–Vis spectroscopy, fieldemission scanning electron microscopy, contact angle measurements and four-point-probe technique for conductivity. Direct morphological observation (FESEM) and electrical measurements indicated that the morphology, conductivity and the nature of deposited PPy films depend on surfactant, surface modification of PET and monomer concentration. In optimized process condition, uniform conductive films of PPy were obtained with good adhesion to PET.     

Preparation and characterization of polypyrrole/magnetite nanocomposites synthesized by in situ chemical oxidative polymerization

This work describes the preparation and characterization of polypyrrole (PPy)/iron oxide nanocomposites fabricated from monodispersed iron oxide nanoparticles in the crystalline form of magnetite (Fe₃O₄) and PPy by in situ chemical oxidative polymerization. Two spherical nanoparticles of magnetite, such as 4 and 8 nm, served as cores were first dispersed in an aqueous solution with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form micelle/magnetite spherical templates that avoid the aggregation of magnetite nanoparticles during the further preparation of nanocomposites. The PPy/magnetite nanocomposites were then synthesized on the surface of the spherical templates. Structural and morphological analysis showed that the fabricated PPy/magnetite nanocomposites are core (magnetite)‐shell (PPy) structures. Morphology of the PPy/magnetite nanocomposites containing monodispersed 4‐nm magnetite nanoparticles shows a remarkable change from spherical to tube‐like structures as the content of nanoparticles increases from 12 to 24 wt %. Conductivities of these PPy/magnetite nanocomposites show significant enhancements when compared with those of PPy without magnetite nanoparticles, in particular the conductivities of 36 wt % PPy/magnetite nanocomposites with 4‐nm magnetite nanoparticles are about six times in magnitude higher than those of PPy without magnetite nanocomposites. These results suggest that the tube‐like structures of 36 wt % PPy/magnetite nanocomposites may be served as conducting network to enhance the conductivity of nanocomposites. The magnetic properties of 24 and 36 wt % PPy/magnetitenanocomposites show ferromagnetic behavior and supermagnetism, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1291–1300, 2008     

Conductivity of Poly(pyrrole)‐Poly(styrene sulfonate) Core–Shell Nanoparticles

The dielectric properties of poly(styrene) nanoparticles decorated at their surfaces with poly(styrene sulfonate) [PSS] brushes and subsequently loaded with polypyrrole (PPy) were studied. These film‐forming materials which may serve as hole‐injection layers in organic light‐emitting diodes, exhibit a core–shell‐type morphology with a core of electrically insulating poly(styrene) and a shell consisting of a corona of PSS chains which form the matrix in which the electrically conducting complex of PPy and PSS is embedded. This conducting complex exists in form of domains of nanoscale dimensions. Thin compressed pellets of these nanoparticles were studied using mainly impedance spectroscopy. Measurements were carried out in the temperature range between 123 and 453 K and frequency range from 10^?1 to 10⁶ Hz. While earlier studies were centered around the effect of polypyrrole volume fraction on the conductivity films and pellets composed of these nanoparticles, the present study reveals in which way the conductivity can be modified by exchange of the mobile inorganic counter ions of PSS. Besides the free‐acid form (H⁺), the Li⁺‐, Na⁺‐ and Cs⁺‐salts of PSS were investigated. The PPy volume fraction was the same for all PPy/PSS core–shell nanoparticles. The distance for phonon‐assisted hopping between next‐neighbor polypyrrolium chains is influenced by the presence of these inorganic cations. For all samples containing PPy, a transition from insulating to conducting behavior in the range of 300‐350 K was found. Using the fluctuation‐induced tunneling model, the average tunneling distance, as well as the potential energy barrier separating neighboring conducting grains was estimated. Finally, a detailed analysis of the dielectric spectra suggests the localization length of the charge carriers to be about 0.33 nm.     

Fabrication and Properties of Conducting Polypyrrole/SWNT‐PABS Composite Films and Nanotubes

We report the electropolymerization and characterization of polypyrrole films doped with poly(m‐aminobenzene sulfonic acid (PABS) functionalized single‐walled nanotubes (SWNT) (PPy/SWNT‐PABS). The negatively charged water‐soluble SWNT‐PABS served as anionic dopant during the electropolymerization to synthesize PPy/SWNT‐PABS composite films. The synthetic, morphological and electrical properties of PPy/SWNT‐PABS films and chloride doped polypyrrole (PPy/Cl) films were compared. Characterization was performed by cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy. SEM and AFM images revealed that the incorporation of SWNT‐PABS significantly altered the morphology of the PPy. Cyclic voltammetry showed improved electrochemical properties of PPy/SWNT‐PABS films as compared to PPy/Cl films. Raman Spectroscopy confirmed the presence of SWNT‐PABS within composite films. Field effect transistor (FET) and electrical characterization studies show that the incorporation of the SWNT‐PABS increased the electronic performance of PPy/SWNT‐PABS films when compared to PPy/Cl films. Finally, we fabricated PPy/SWNT‐PABS nanotubes which may lead to potential applications to sensors and other electronic devices.     

Pt and Pt–Ru nanoparticles decorated polypyrrole/multiwalled carbon nanotubes and their catalytic activity towards methanol oxidation

Conducting polymer composite films comprised of polypyrrole (PPy) and multiwalled carbon nanotubes (MWCNTs) [PPy–CNT] were synthesized by in situ polymerization of pyrrole on carbon nanotubes in 0.1 M HCl containing (NH₄)S₂O₈ as oxidizing agent over a temperature range of 0–5 °C. Pt nanoparticles are deposited on PPy–CNT composite films by chemical reduction of H₂PtCl₆ using HCHO as reducing agent at pH = 11 [Pt/PPy–CNT]. The presence of MWCNTs leads to higher activity, which might be due to the increase of electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces allowing higher dispersion and utilization of the deposited Pt nanoparticles. A comparative investigation was carried out using Pt–Ru nanoparticles decorated PPy–CNT composites. Cyclic voltammetry demonstrated that the synthesized Pt–Ru/PPy–CNT catalysts exhibited higher catalytic activity for methanol oxidation than Pt/PPy–CNT catalyst. Such kinds of Pt and Pt–Ru particles deposited on PPy–CNT composite polymer films exhibit excellent catalytic activity and stability towards methanol oxidation, which indicates that the composite films is more promising support material for fuel cell applications.     

Characteristics of polypyrrole electrodeposited onto roughened substrates composed of gold–silver bimetallic nanoparticles

In this work, the characteristics of polypyrrole (PPy) films electrodeposited onto an electrochemically roughened gold substrate with bimetallic silver and gold nanoparticles were first investigated. First, a silver substrate was roughened by a triangular‐wave oxidation–reduction cycle (ORC) in an aqueous solution containing 0.1 M HCl. Subsequently, a gold substrate was roughened by a similar ORC treatment in this used solution. The results revealed that the surface of the roughened gold substrate demonstrated two different kinds of deposition domains because of the modification of silver nanoparticles. Encouragingly, some novel characteristics of PPy deposited onto this substrate were observed, in comparison with those on the roughened gold substrate without the modification of silver nanoparticles. They included a denser and more compact surface morphology, higher oxidation degree, increased conductivity, and improved surface‐enhanced Raman scattering. Furthermore, the nucleation and growth mechanism for PPy electropolymerization on this silver‐modified roughened gold substrate was distinguishable from that on the unmodified one. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2724–2731, 2006     

Effect of ammonia on the temperature‐dependent conductivity and thermopower of polypyrrole

We report the first measurements of the effect of ammonia gas on the temperature dependence of the conductivity and thermoelectric power of polypyrrole films. Our data are for samples of very different conductivities, extending down to a temperature of 200 K for low‐conductivity polypyrrole gas sensors, and down to 4.2 K for more highly‐conducting PPy(PF₆) samples. We demonstrate that (except for the most metallic case) our polypyrrole samples show greater sensitivity to ammonia as the temperature is lowered (i.e. the fractional reduction in conductivity is greater at lower temperatures). Remanent decreases in conductivity are present after the removal of ammonia for higher pressure exposures, and remanent increases in the metal‐like thermoelectric power for the PPy(PF₆) for samples grown at higher temperatures. Our results indicate that the mechanism of this conductivity decrease in PPy(PF₆) is that ammonia causes a reduction in the size of metallic regions as disordered barrier regions are thickened. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1331–1338, 2006     

Effects of Reaction Sequence on the Colloidal Polypyrrole Nanostructures and Conductivity

The relationship between nanoscaled morphology and macroscopic electrical conductivity of polypyrrole (PPy) nanostructures was qualitatively investigated. The PPy nanostructures were prepared via microemulsion polymerization using ionic surfactants. The morphology of PPy was influenced by both the type of ionic surfactants and reaction sequences; specifically, the PPy structures were highly influenced by the reaction sequence when anionic surfactant of SDS was used. By changing reaction sequence, a gel-like PPy was formed influencing on the macroscopic electrical conductivity. The results indicate that the macroscopic conductivity of PPy is affected by its nanoscaled structures as determined by the reaction conditions.     

Characteristics of the ring stretching of oxidized polypyrrole on the surface-enhanced Raman spectrum

In this study, polypyrrole (PPy) films were electropolymerized under different preparation conditions on rough gold substrates. The peak shown at the higher frequency of the double peaks at about 1329 and 1386 cm^–1 in surface-enhanced Raman scattering of PPy was initially assigned to the ring stretching of oxidized PPy. A systematic study was carried out to confirm this assignment. It was found that the conductivity of PPy was strongly related to and increased with this Raman peak intensity of oxidized PPy. Meanwhile, the normalized relative intensities of this Raman peak for various PPy films are consistent with their corresponding doping levels. Electronic Publication     

Synthesis and characterization of conductive polypyrrole grown on the sulfonated surface of polyethylene films

Chemical synthesis of polypyrrole (PPy) was carried out in the presence of FeCl₃ aqueous solution. The grown PPy is fixed on the sulfonated surface of polyethylene (SPE) films, where the sulfonic groups act as counteranions to balance the positive charge of PPy, giving the composite material of PPy–SPE. For reasons of comparison, two types of polyethylene (PE) have been used, low and high densities with different degrees of sulfonation, SD (g/m²), defined as the ratio of weight increase to the area of the two surfaces of the sample. A series of reaction times was used to evaluate the variation of the electrical conductivity, σ (S/cm), of polypyrrole. It was found that σ increases as reaction time increases. To characterize the samples, Fourier transform infrared (FTIR) spectroscopy and conductivity measurements were performed.     

Conductivity enhancement in raw polypyrrole and polypyrrole nanoparticle dispersions

For certain commercial applications of polypyrrole (PPy), an enhancement of the electrical conductivity of the material is the key to industrial success. In this paper it will be shown that raw PPy with high conductivity (>150 S/cm) can be obtained in very good yield (>90%) by appropriate selection of both bi‐functional additives and reaction conditions which increase the oxidative polymerization rate of pyrrole. The presence of new active centers for the polymerization is demonstrated by UV measurements. In addition, raw PPy synthesized according to the improved method of synthesis shows good stability of the conductivity upon aging at high temperature (150°C) in air. Finally, new PPy dispersions are reported with an average particle size of 67 nm obtained by sonochemical synthesis that can be incorporated into conventional plastic paints for direct metallization of plastics. The conductivity of the new metallization paint developed was 0.4 S/cm with a PPy content of 10 wt%. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Polypyrrole Nanoparticles and Their Nanocomposites with Poly(propylene)

Summary: Conducting polypyrrole (PPy) nanoparticles were synthesized via microemulsion polymerization. PP/PPy nanocomposites were prepared by melt-mixing of polypyrrole with polypropylene (PP) and processed with injection molding. Tensile tests have revealed that increasing amount of PPy increased the strength and the stiffness of the nanocomposite while limiting the elongation of PP. Thermal gravimetric analysis has showed that incorporation of PPy nanoparticles has improved the thermal stability of the nanocomposites. Increasing amount of PPy nanoparticles increases the conductivity of nonconductive PP up to 2,4.10⁻⁴ Scm⁻¹. The same techniques were used to characterize nanocomposites containing 2% w dispersant. Composites prepared with dispersant have involved smaller dimension PPy nanoparticles and exhibited improvement in some mechanical and thermal properties.     

Paper-like free-standing polypyrrole and polypyrrole–LiFePO4 composite films for flexible and bendable rechargeable battery

Highly flexible, paper-like, free-standing polypyrrole and polypyrrole–LiFePO₄ composite films were prepared using the electropolymerization method. The films are soft, lightweight, mechanically robust and highly electrically conductivity. The electrochemical behavior of the free-standing films was examined against lithium counter electrode. The electrochemical performance of the free-standing pure PPy electrode was improved by incorporating the most promising cathode material, LiFePO₄, into the PPy films. The cell with PPy–LiFePO₄ composite film had a higher discharge capacity beyond 50 cycles (80 mA h/g) than that of the cell with pure PPy (60 mA h/g). The free-standing films can be used as electrode materials to satisfy the new market demand for flexible and bendable batteries that are suitable for the various types of design and power needs of soft portable electronic equipment.     

ZnO/PPy异质纳米复合材料的制备、表征及其气敏特性

室温下, 采用原位聚合法, 以吡咯(PY)为单体, 氯化铁(FeCl₃·6H₂O)为氧化剂, 在塑料基片上聚合生长了聚吡咯(PPy)纳米微球. 然后在聚吡咯基片上生长ZnO种子, 将表面种有ZnO种子的PPy元件置于六次甲基四胺与硝酸锌的混合溶液中, 90 ℃水浴中, 在PPy微球上生长了ZnO纳米棒, 合成了PPy/ZnO异质纳米复合材料. 分别通过X射线衍射仪(XRD)和场发射扫描电镜(FESEM)对PPy/ZnO异质纳米复合材料的结构和形貌进行了表征. 制备了塑料基的PPy/ZnO异质纳米复合材料气体传感器, 在室温下, 对10×10^-6-150×10^-6 (体积分数)浓度范围的氨气进行了气敏测试, PPy/ZnO气敏元件对氨气响应的灵敏度基本呈线性关系, 且对甲醇、丙酮、甲苯等有机气体表现出很好的选择性. 最后, 对PPy/ZnO异质纳米复合材料的形成机理进行了简要分析.     

Highly conductive free standing polypyrrole films prepared by freezing interfacial polymerization

Highly conductive free standing polypyrrole (PPy) films were prepared by a novel freezing interfacial polymerization method. The films exhibit metallic luster and electrical conductivity up to 2000 S cm(-1). By characterizing with SEM, FTIR, Raman and XRD, the high conductivity is attributed to the smooth surface, higher conjugation length and more ordered molecular structure of PPy.     

Electrochromic properties of Prussian blue–polypyrrole composite films in dependence on parameters of synthetic procedure

Composite materials of Prussian blue–polypyrrole (PB/PPy) on the surface of indium tin oxide (ITO)-coated glasses were obtained via one-step chemical (redox) and one-stage electrochemical procedures in mixed solution of iron (III), hexacyanoferrate (III), and pyrrole with various concentration ratios of components in nitrate supporting electrolyte. Electrochemical stability of composite films depends on the amount of Py in synthetic solution, whereas color contrast coefficient values depend on the type of synthetic procedure. PB/PPy film electrochromic response (tested by spectroelectrochemical potentiodynamic measurements) was compared with response of both pure PB and pure PPy films. It was shown that degradation of composite films occurs due to PB component instability in Prussian white form. The highest value of color contrast coefficient and great electrochemical stability were revealed for composite films obtained via redox-synthesis procedure from solution with 0.1 mM [Fe³⁺ + Fe(CN)₆ ^3?] and 1.0 mM Ру (PB/PPy-Ch-1:1:10 system).     

Thermal decomposition of polypyrroles

The thermal stability of polypyrrole (PPy) samples has been studied by thermogravimetry/mass spectrometry and pyrolysis-gas chromatography/mass spectrometry in inert atmospheres. PPy has been prepared by chemical oxidative polymerization using ferric sulfate as an oxidant and anionic surfactants, such as dodecylbenzenesulfonic acid and sodium dodecylbenzenesulfonate as co-dopants. For comparison we have studied polypyrrole (PPy-SO₄) prepared without any additive. It was found that the presence of anionic surfactants improved the thermal stability of PPy. The decomposition of PPy doped with ferric sulfate and anionic surfactants occurs at relatively high temperature indicating that chemical interactions exist between the polymer and the surfactants.     

New biocompatible polypyrrole-based films with good blood compatibility and high electrical conductivity

A novel O-butyryl chitosan (OBCS)-grafted polypyrrole (PPy) film was described. The immobilization was accomplished by photocrosslinking the OBCS onto PPy films under ultraviolet light irradiation. The surfaces of OBCS-grafted PPy film were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and electron spectroscopy for chemical analysis (ESCA). The blood compatibility of the OBCS-grafted PPy film was evaluated by platelet-rich plasma (PRP) contacting experiments and protein adsorption experiments in vitro. These results have demonstrated that the surface with immobilized OBCS shows much less platelet adhesive and fibrinogen adsorption compared to the control surface. The bulk conductivity values of PPy films were measured by a modified four-probe method. The composite films have both good blood compatibility and high electrical conductivity that make them suitable for using as potential biomaterials, such as electrically conducting blood vessel and functionally haemocompatible substrate of biosensor used directly in whole blood.     

Controllable fabrication of porous free-standing polypyrrole films via a gas phase polymerization

A facile gas phase polymerization method has been proposed in this work to fabricate porous free-standing polypyrrole (PPy) films. In the presence of pyrrole vapor, the films are obtained in the gas/water interface spontaneously through the interface polymerization with the oxidant of FeCl(3) in the water. Both the thickness of the film and the size of the pores could be controlled by adjusting the concentrations of the oxidant and the reaction time. The as-prepared PPy films exhibited a superhydrophilic behavior due to its composition and porous structures. We have demonstrated a possible formation mechanism for the porous free-standing PPy films. This gas phase polymerization is shown to be readily scalable to prepare large area of PPy films.     

Preparation of Polypyrrole/Poly(methyl methacrylate) Core-Shell Nanoparticles in Four-Component Microemulsion Media

Electrically conductive polypyrrole (PPy)/poly(methyl methacrylate) (PMMA) core-shell nanoparticles were synthesized by two-step microemulsion polymerization. PPy core particles were prepared in a four-component microemulsion system, which was formed with surfactant cetyltrimethyl ammonium bromide (CTAB), cosurfactant n-pentanol, water, and pyrrole. Ferric chloride and iodine was added as the oxidant and the dopant, respectively. Then the PPy nanoparticles were coated with PMMA to prepare PPy/PMMA core-shell nanoparticles. The morphology of PPy/PMMA core-shell nanoparticles was characterized with transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy was used to characterize the structure of the samples. The electrical conductivities of samples were studied by a Hall effect testing instrument. Despite being coated with a layer of insulation, the conductivity of the composite PPy/PMMA core-shell nanoparticles could still reached to 7.856 × 10^?1 S/cm.