Conductive spherical polypyrrole nanoparticles were obtained by polymerization in oil-in-water (o/w) microemulsions using
sodium dodecyl sulfate (SDS) as anionic surfactant, ethanol as co-surfactant, and potassium persulfate (KPS, 0.017 wt.%) as
oxidizing agent. The average particle diameter (Dp) of the nanoparticles was between 38 and 45 nm with narrow particle size
distributions (Dw/Dn < 1.2). Dp increases with the ethanol concentration due to the intercalation between the polar heads of SDS, promoting instability
of the nanoparticles and some coagulation. In this work, low surfactant concentration was used, and the molar ratio of the
oxidizing agent to monomer was 8.5 × 10−3, a value much lower compared with others reported in the literature. Increasing the ethanol concentration in the recipes
enhanced the conductive properties of the polymers due to the high π-conjugation length obtained. 相似文献
Conducting bacterial cellulose (BC) membranes coated with a high proportion of polyaniline (PAni) were prepared through in situ oxidative polymerization of aniline on the surface of the BC in the presence of acetic acid as the protonating agent. The effect of two different oxidizing agents, ammonium persulfate (APS) or iron(III) chloride (FeCl3), on the mechanical performance, electrical conductivity, crystallinity, morphology and ability to absorb the electromagnetic radiation was investigated. BC/PAni membranes prepared with FeCl3 displayed higher conductivity and better mechanical performance than those observed for pure BC or the BC/PAni membranes prepared with APS. Experiments related to the electromagnetic absorbing properties revealed that BC/PAni membranes prepared with FeCl3 also present improved absorbing properties in the frequency range of 8–12 GHz. The morphology of the membranes, observed by field emission gun-scanning electron microscopy, is strongly affected by the oxidizing agent. Whereas the BC/PAni membranes prepared with APS present PAni nanoparticles attached on the fiber surface as agglomerates in the form of flakes, those prepared with FeCl3 display a uniform and smooth coating of PAni on the BC fibers as hierarchical mode. 相似文献
Nafion 117 membranes were modified with a thin film of poly(3,4-ethylenedioxythiophene) (PEDOT) by a diffusion-controlled polymerization process using a two-compartment cell with the monomer EDOT on one side of the membrane and the oxidizing agent FeCl3 on the other side. The methanol permeability and ion conductivity of the composite PEDOT/Nafion membranes were measured as a function of temperature and polymerization time by DC and AC polarization measurements in four-electrode technique and permeation experiments in a diaphragm cell. These modified membranes have lower methanol permeability while maintaining adequate conductivity. 相似文献
Summary: Electrically conducting polypyrrole‐poly(ethylene oxide) (PPy‐PEO) composite nanofibers are fabricated via a two‐step process. First, FeCl3‐containing PEO nanofibers are produced by electrospinning. Second, the PEO‐FeCl3 electrospun fibers are exposed to pyrrole vapor for the synthesis of polypyrrole. The vapor phase polymerization occurs through the diffusion of pyrrole monomer into the nanofibers. The collected non‐woven fiber mat is composed of 96 ± 30 nm diameter PPy‐PEO nanofibers. FT‐IR, XPS, and conductivity measurements confirm polypyrrole synthesis in the nanofiber.
An SEM image of the PPy‐PEO composite nanofibers. The scale bar in the image is 500 nm. 相似文献
Poly(o-phenylenediamine) (PoPD) hollow spheres (ca. 800 nm in outer diameter) were synthesized by a simple solution route using ammonium persulfate (APS) as the oxidizing agent, whereas PoPD nanofibers (0.5-2 μm in width and more than 100 μm in length) and gold nanoparticles (200-500 nm) were obtained when changing the oxidizing agent of APS to chlorauric acid (HAuCl4). The chemical structures of PoPD hollow spheres and nanofibers were characterized by FTIR and XRD spectra. When using HAuCl4 as the oxidizing agent, the products of PoPD nanofibers and gold nanoparticles could be separated by chemical methods. The monomer droplets were proposed to act as template to the formation of polymer hollow spheres while the oriented growth of polymer nanofibers might be catalyzed by gold nanoparticles. 相似文献
Composite films of polyethylene (PE) and polypyrrole (PPy) were prepared by polymerization of PPy on an ultradrawn polyethylene film with high modulus and high strength in ferric chloride (FeCl3) aqueous solution. The electrical conductivity of the composite film was found to be related to the polymerization conditions, such as polymerization temperature, polymerization time, the concentration and the oxidation potential of the FeCl3 solution. Scanning electron microscopy, FTIR and 13C NMR spectra were used to elucidate the morphological and structural variations of PPy prepared under different conditions, which lead to the differences in the electrical properties of the resultant composite films. The best electrical conductivity of the composite was about 5.5 S/cm for the film prepared under optimum conditions. The Young's modulus and the tensile strength reached 80 GPa and 3.2 GPa, respectively, which indicated the successful production of a conductive polymer with high strength and high modulus. 相似文献
Silicon (Si) nanoparticles were stabilized by sodium dodecyl sulfate and poly(N-vinylpyrrolidone) in water, and coated with polypyrrole (PPy) via in situ polymerization of pyrrole with FeCl3. TEM images revealed that the Si nanoparticles were successfully coated with PPy (average thickness, ∼2 nm). The Li/PPy-coated Si electrode exhibited improved discharge capacities, compared to that of a reported Li/pure Si electrode, even though the capacity fading problem caused by large-scaled crumbling of the electrode was not overcome. 相似文献
The previously found strong dependence of the polymerization enthalpy on the reaction temperature has been rationalized. The temperature dependence is to be ascribed to the existence of a ‘ceiling temperature’ for the polymerization process of the pyrrole monomer. The determined ceiling temperature has beenT?350 K when FeCl3 was used as the oxidizing agent in CH3CN solution. The existence of a ceiling temperature together with its already determined exoenthalpic nature allows to classify the polymerization reaction as an exoentropic one. From the dependence of the yield of insoluble polymer on the reaction temperature, the trend of the relative mean numeral molecular massMn for the different obtained polymers has been determined. Measurements of electrical conductivity on pressed pellets of the different polymers allowed to establish a correlation between theMn value and the conductivities The dependence of the conductivity on the exposition time to the air allowed to do some essays on the aging behaviour of the obtained polypyrrole. By making some assumptions, an absolute calorimetric determination of the value ofMn of polypyrrole was tempted together with that of the related poly-N-vinilpyrrole. 相似文献
In this study, nanostructure polyaniline was prepared from aniline monomer via chemical oxidative polymerization in the presence of ammonium persulfate as an oxidizing agent. Interfacial, emulsion, rapid mixing and ultrasonic techniques are used for polymer synthesis. In the interfacial method, chloroform, n-hexane, hexanole and toluene were used as organic solvents and sulfuric acid, methane sulfonic acid and acetic acid were employed as electrolyte solutions. In the emulsion polymerization, dodecyl benzene sulfonic acid and aqueous solution of hydrochloric acid were used as emulsion agent and electrolyte solution respectively. In rapid mixing reaction and ultrasonic method, hydrochloric acid and salicylic acid were used as dopants. The structure, conductivity, morphology and particle size distribution of prepared polymers were investigated after purification and drying by FTIR spectroscopy, scanning electron microscopy and electrical conductivity measurements. 相似文献
Magnetically loaded polymeric nano-particles carrying functional groups on their surface were prepared by a two-stage process. In the first stage, super-paramagnetic magnetite (Fe3O4) nano-particles were produced by a co-precipitation method from the aqueous solutions of FeCl2·4H2O and FeCl3·6H2O using a NaOH solution. The smallest size obtained was 40.9 nm with poly-dispersity index of 0.194 obtained by using a Zeta Sizer. The effects of Fe2+/Fe3+ molar ratio, stirring rate, temperature, base concentration, and pH on the particle size/size distribution and stability of the dispersions were examined. Increasing the relative concentration of Fe2+ ion and decreasing the stirring rate and pH increased the particle size, while the concentration of NaOH and temperature did not change the particle size significantly. Polymer coating was achieved by emulsion polymerization at high surfactant to monomer ratio of methyl methacrylate (MMA) and acrylic acid which were used as comonomers (comonomer ratio: 90/10 weight) with high surfactant to monomer ratio. The surfactant and initiator were SDS and KPS, respectively. Nano-particles in the range of 115 and 300 nm in diameter were produced depending on recipe. Increasing the Fe3O4/monomer and surfactant/monomer ratios, the KPS concentration caused a decrease in the average diameter. Magnetic properties of the nano-particles were obtained by electron spin resonance and vibrating-sample magnetometer. Most of the polymer-coated nano-particles exhibited super paramagnetic behavior.An erratum to this article can be found at 相似文献
Wire-, ribbon-, and sphere-like nanostructures of polypyrrole have been synthesized by solution chemistry methods in the presence of various surfactants (anionic, cationic, or nonionic surfactant) with various oxidizing agents [ammonium persulfate (APS) or ferric chloride (FeCl3), respectively]. The surfactants and oxidizing agents used in this study have played a key role in tailoring the nanostructures of polypyrrole during the polymerization. It is inferred that the lamellar structures of a mesophase are formed by self-assembly between the cations of a long chain cationic surfactant [cetyltrimethylammonium bromide (CTAB) or dodeyltrimethylammonium bromide (DTAB)] and anions of oxidizing agent APS. These layered mesostructures are presumed to act as templates for the formation of wire- and ribbon-like polypyrrole nanostructures. In contrast, if a short chain cationic surfactant octyltrimethylammonium bromide (OTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonylphenyl ether (Opi-10) is used, sphere-like polypyrrole nanostructures are obtained, whichever of the oxidizing agents mentioned above is used. In this case, micelles resulting from self-assembly among surfactant molecules are envisaged to serve as the templates while the polymerization happens. It is also noted that, if anionic surfactant sodium dodeyl surfate (SDS) is used, no characteristic nanostructures of polypyrrole were observed. This may be attributed to the doping effect of anionic surfactants into the resulting polypyrrole chains, and as a result, micelles self-assembled among surfactant molecules are broken down during the polymerization. The effects of monomer concentration, surfactant concentration, and surfactant chain length on the morphologies of the resulting polypyrrole have been investigated in detail. The molecular structures, composition, and electrical properties of the nanostructured polypyrrole have also been investigated in this study. 相似文献
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. 相似文献