PPy Loading Research Articles

Synthesis of fly-ash cenospheres coated with polypyrrole using a layer-by-layer method

Uniform polypyrrole (PPy) films, of controlled thickness, were successfully synthesized and immobilized on polyelectrolyte (PE) multilayer-assembled fly-ash cenospheres (FACs) using a simple and versatile method. In this approach, FACs were assembled with multilayers of poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) using a layer-by-layer self-assembly procedure. The FACs were used as templates for the subsequent deposition of PPy. The deposition behaviours of PEs on the surfaces of the FACs were examined, and the results could be fitted to a first-order exponential decay model at pH 6. The surfaces of the PE-deposited FACs (FAC-(PDDA-PSS)n, n is the number of PE layers) became more homogeneous as n increased. Their properties were determined mainly by the PE, not by the FAC itself, after n = 4. PPy-coated FACs with PE precursor layers [(PPy/FAC-(PDDA-PSS)n] had different morphologies for different numbers of PE layers. The PPy loading amount on the FACs and the conductivities of the composites reached plateaus after the PE layer deposition number exceeded six.

Synthesis of P(St-MAA)-Fe3O4/PPy core–shell composite microspheres with conductivity and superparamagnetic behaviors

Styrene (St) and methacrylic acid (MAA) copolymers were synthesized by emulsion polymerization using Fe3O4 particles modified by oleic acid as central components. P(St-MAA)-Fe3O4/PPy (polypyrrole) core–shell composite microspheres with conducting and supermagnetic behaviors were obtained via in situ chemical oxidative polymerization on the surface of the P(St-MAA)-Fe3O4 magnetic composite microspheres. The –COOH groups in the composites acted as co-dopants in the formation of PPy and adsorbed the pyrrole monomers onto the surface of P(St-MAA)-Fe3O4. The P(St-MAA)-Fe3O4/PPy composite microspheres have been extensively characterized by transmission electron microscope (TEM), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The Fe3O4 particles were coated within P(St-MAA) polymers when the volume ratio of MAA to St was maintained at 1:5 during the co-polymerization process. The P(St-MAA)-Fe3O4/PPy multi-component composite microspheres show excellent superparamagnetism. The electrical conductivity of the composite microspheres largely depended on the PPy loading amount in the outer layer.

Composite polypyrrole-containing particles and electrical properties of thin films prepared therefrom

Preparation of core–shell particles consisting of polystyrene–poly(ethylene glycol) monomethacrylate (PS–PEGMA) core covered with polypyrrole (PPy) shell is described. The thickness of PPy shell, which strongly influences electrical properties of the films prepared from the particles, can be varied by changing pyrrole load, controlling the overall template surface area in the system and by influencing the pyrrole polymerization kinetics in the presence of different oxidants. The type of anions and PPy loading strongly influence the electrical conductivity. Typical value of the resistivity of thin film consisting of core–shell particles was 34Ωm (PPy oxidized by FeCl3, shell thickness 3nm). Current–voltage dependences of low conductivity samples (thin PPy shell layer) are characteristic of contact-limited currents. The conductivity of the particles changes with humidity, which can be utilized in humidity sensors.

Electrochemical Behaviour of Platinum Nanoparticles Supported on Polypyrrole (PPy)/C Composite

We report on the synthesis of composites Polypyrrole/Carbon (PPy/C) to be used as matrix-support of platinum nanoparticles prepared by carbonyl chemical route. The composite materials with different PPy loading were characterized by physical chemical methods, such as elemental analysis, infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The catalysts: 20 wt. % Pt/composites were used as substrates for the oxygen reduction reaction in acid medium. For the same catalyst loading (50 µg cm-2), it was observed that the nature of the composite strongly influences the electrochemical activity of nanoparticulated platinum.

THE EFFECT OF POLYPYRROLE LOADING ON THE ELECTRORHEOLOGICAL PROPERTIES OF POLYPYRROLE/SBA-15 SUSPENSIONS

Encapsulated polypyrrole (PPy) with different amount in the channels of mesoporous silica (SBA-15) was synthesized. The XRD and N 2 adsorption/desorption isotherms analysis show that PPy with different loadings in the channels does not affect the ordered hexagonal structure of resultant PPy/SBA-15 nanocomposites. Further, the electrorheological (ER) properties of the nanocomposites with different PPy loadings were investigated by steady and oscillatory shear experiments. The results reveal that PPy/SBA-15 fluids exhibit typical ER and viscoelastic behavior under the applied electric field and ER response depends mainly on PPy loadings and there is an optimum PPy loading for strong ER effect.

Preparation, surface chemistry, and electrical conductivity of novel silicon carbide/polypyrrole composites containing an anionic surfactant

AbstractNovel silicon carbide/polypyrrole (SiC/PPy) conducting composites were prepared using silicon carbide as inorganic substrate in the presence or absence of an anionic surfactant, dodecylbenzenesulfonic acid (DBSA). The surface modification of SiC particles was performed in aqueous solution containing the anionic surfactant by oxidative polymerization of pyrrole using ferric chloride as oxidant. Ash content analysis was used to determine the mass loading of organic fraction in the SiC/PPy composites. Scanning electron microscopy showed the surface modification of SiC by PPy. The presence of PPy in the composites was confirmed by infrared spectroscopy. The small gradual red shift of the band of the stretching vibrations of SiCO and SiOSi bonds and more intensive of PPy spectrum were observed when DBSA was used for composite preparation. The presence of both polypyrrole and surfactant was also detected by their respective N1s and S2p core level peaks recorded by X‐ray photoelectron spectroscopy. The electrical conductivity of SiC‐DBSA/PPy composites depends on PPy content at the surface and on pyrrole/DBSA molar ratio. The DBSA‐containing composites have a conductivity about 2 orders of magnitude higher than in the case of the composites prepared without DBSA when PPy loading was lower than 15 wt%. Above this PPy loading the difference in conductivity almost diminished due to a increased amount of PPy polymerized on the surface of the SiC substrate. SiC‐DBSA/PPy composites containing 15 wt% PPy prepared using a molar ratio pyrrole/DBSA = 5, exhibited a very hydrophobic behavior compared to the corresponding DBSA‐free composites, as they floated on water and did not sediment even after a prolonged period of time. POLYM. ENG. SCI., 47:1198–1206, 2007. © 2007 Society of Plastics Engineers

Preparation and characterization of Pt direct deposition on polypyrrole modified Nafion composite membranes for direct methanol fuel cell applications

A novel method of Pt catalyst direct deposition on polypyrrole (ppy)-modified Nafion composite membranes for direct methanol fuel cell (DMFC) is proposed in this paper. Proton conductivity and methanol permeability of polypyrrole-modified Nafion composite membranes were investigated. The Pt particles were directly deposited on the PPy-modified Nafion composite membranes by using chemical reduction of platinic chloride at room temperature. Scanning electron microscopy measurements showed that Pt particles with a porous structure uniformly exist in the Pt/PPy/Nafion electrodes. The roughness factor and the active surface area of the Pt catalyst increased with increasing PPy loading. The performance of the Pt/PPy/Nafion electrodes was evaluated in a single DMFC.

Synthesis and interfacial properties of montmorillonite/polypyrrole nanocomposites

Montmorillonite/polypyrrole (MMT/PPy) nanocomposites were prepared by the in situ polymerization of pyrrole in the presence of MMT. The morphology of the MMT/PPy nanocomposites as examined by scanning electron microscopy differs slightly from that of the untreated MMT but markedly from that of polypyrrole. X-ray photoelectron spectroscopy (XPS) showed that the materials have MMT-rich surfaces, an indication that polypyrrole is essentially intercalated in the host clay galleries. The transmission electron microscopy showed, that the interlamellar spacing of the untreated MMT increased from 1.25 to 18.9 nm, when compared to nanocomposite MMT/10.8% PPy. Moreover, XPS highlighted the cation exchange of Na + from montmorillonite by K + (from the oxidant) and by the positively charged polypyrrole chains. Inverse gas chromatography indicated that the nanocomposites are high surface energy materials with a dispersive contribution to the surface energy ( γ S d ) reaching 200 mJ/m 2 at 150 °C, for a PPy loading of 21.4 wt%. The ( γ S d ) values of the MMT/PPy nanocomposites were correlated to the changes in the specific surface area of the MMT induced by the intercalation of polypyrrole.

Synthesis and evaluation of conducting polypyrrole/Al 2O 3 nanocomposites in aqueous and non-aqueous medium

The polymerization of pyrrole (PY) in aqueous or alcohol/water mixed medium in presence of FeCl 3 and nanodimensional Al 2O 3 resulted in the formation of conducting nanocomposites of polypyrrole (PPY)/Al 2O 3. The incorporation of PPY in the composites was endorsed by FT-IR studies. The extent of PPY loading in the composites decreased with increasing amount of Al 2O 3 in the initial feed at a fixed PY and FeCl 3 amount, respectively. For alcohol–water systems, the extent of PPY loading in the composites decreased with increasing alcohol concentration in the mixture with fixed amount of Al 2O 3, FeCl 3 and PY, respectively. SEM and TEM studies revealed interesting morphological features for the composites prepared under various conditions and confirmed the formation of monodispersed composite particles of diameters in the nanometer range. TG analyses revealed the enhanced thermal stabilities of the nanocomposites relative to the base polymer. The dc conductivities of the PPY/Al 2O 3 nanocomposites were in the order of (63±3 to 33±5)×10 −2 S/cm, and the values increasing with decreasing Al 2O 3 loading in the nanocomposites in aqueous medium but in case of alcohol–water medium, dc conductivities increases with increasing alcohol content in the medium. Some of these nanocomposites could be obtained as stable dispersion during synthesis.

Preparation and evaluation of composites from montmorillonite and some heterocyclic polymers: 3. a water dispersible nanocomposite from pyrrole-montmorillonite polymerization system

Montmorillonite (MMT)-based nanocomposites of polypyrrole (PPY) were prepared through the polymerization of pyrrole with MMT and FeCl 3-impregnated MMT in bulk and in aqueous medium. The composites were characterized by IR, X-ray diffraction (XRD), and scanning electron microscopy (SEM) studies. XRD analyses revealed no change in d 001 spacing in MMT (9.8 Å), suggesting no intercalation of PPY into MMT lamellae. TEM analysis indicated the particle size to be 25 ± 7 nm. The bulk conductivity of the composites was in the range of (1.3 to 26) × 10 −5 S/cm, depending on the FeCl 3-impregnation level and on the PPY loading in the composites. Suitable procedures were developed for obtaining a stable aqueous dispersion and a reversible dispersion of these composites.

X-ray Photoelectron Spectroscopy Characterization of Submicrometer-Sized Polypyrrole−Polystyrene Composites

The surface compositions of a series of five polystyrene−polypyrrole (PS−PPy) composites and three reference materials (the original poly(ethylene glycol) (PEG) stabilizer, the uncoated PEG-stabilized PS latex, and PPy chloride bulk powder) were examined by X-ray photoelectron spectroscopy (XPS). The uncoated PEG-stabilized PS latex particles had a narrow size distribution with a mean diameter of 129 nm. The N1s XPS signal is a unique elemental marker for the PPy component and was therefore used to determine its surface concentration. As the PPy loading on the PS latex particles was increased from 4.2 to 28.1 wt % the relative intensity of the N1s signal increased, as expected. However, surface doping levels calculated from the Cl/N atomic ratios were relatively low, suggesting that some oxidative degradation of the deposited PPy component had occurred. Raman studies also indicated decreased doping levels at low PPy loadings. Close inspection of the C1s envelopes indicated that the composite particles did not have the expected core−shell morphology, since even at the highest PPy loading these XPS spectra were very similar to that of the original PS latex. These observations were confirmed by scanning electron microscopy (SEM) studies, which revealed the presence of discrete PPy nanoparticles of 20−30 nm diameter. Finally, it was found that more uniform PPy overlayers could be prepared by modifying the synthesis conditions. Thus, reducing both the total latex surface area and the pyrrole monomer concentration led to PS−PPy particles with a much improved core−shell morphology, as judged by both XPS and SEM.