Polypyrrole Particles Research Articles

Preparation of conductive polypyrrole (PPy) composites under supercritical carbon dioxide conditions

Electrically conductive composites were prepared via the chemical oxidative polymerization of the pyrrole monomer in polystyrene (PS) and zinc neutralized sulfonated polystyrene (Zn-SPS) films under supercritical carbon dioxide (SC-CO2) conditions. The strong swelling effect of SC-CO2 made polypyrrole (PPy) particles not only form on the surface, but also become incorporated into the film, resulting in a homogeneous structure with a relatively higher conductivity. By comparison, the composite prepared in aqueous solutions shows a skin-core structure and a conductivity of 3 to 4 orders of magnitude lower than that of the former due to the diffusion-controlled process of the pyrrole monomer. The percolation thresholds of PS/PPy and Zn-SPS/PPy composites were 6.2% and 2.7% of the volume fraction of PPy, respectively, much lower than the theoretically predicted value of 16%. Moreover, the conductive composites prepared under SC-CO2 conditions showed higher thermal stability, especially in the high-temperature region.

Synthesis and characterization of Ag/polypyrrole nanocomposites based on silver nanoparticles colloid

Ag/polypyrrole nanocomposites were successfully synthesized via in situ chemical oxidation polymerization of pyrrole based on mercaptocarboxylic acid capped Ag nanoparticles colloid. Scanning electron microscopy (SEM) measurement showed that the obtained Ag/polypyrrole nanocomposites were spherical. Transmission electron microscopy (TEM) measurement showed that the Ag nanoparticles were inside the polypyrrole particles and had a little aggregation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra were used to characterize the structure of the obtained Ag/polypyrrole nanocomposites. A possible formation mechanism of the Ag/polyrrole nanocomposites was also proposed.

Preparation of Polypyrrole by Emulsion Polymerization Using Hydroxypropyl Cellulose

Polypyrrole with particles of uniform diameter was easily obtained from an emulsion of hydroxypropyl cellulose (HPC) and pyrrole by chemical oxidative polymerization, using iron chloride as an oxidizing agent. The particle diameter of the polypyrrole could be controlled by changing the HPC concentration, and it was found that the preparation of water-dispersible polypyrrole was possible. The conductivity of the polypyrrole particles was of the order of 10−1 S/cm.

Electrically Conductive Poly(DL-lactide)/Chitosan/Polypyrrole Complexes

Summary: The fabrication of novel conductive poly(DL-lactide)/chitosan/polypyrrole complex membranes is reported. Using poly(DL-lactide)/chitosan blends as matrices and polypyrrole as a conductive component, several kinds of membranes with various compositions are prepared. A percolation threshold of polypyrrole as low as 1.8 wt.-% is achieved for some membranes by controlling the chitosan proportion between 40 and 50 wt.-%. SEM images exhibit that the membranes with a low percolation threshold show a two-phase structure which consists of poly(DL-lactide) and chitosan phases. Dielectric measurements indicate that there is limited miscibility between the poly(DL-lactide) and chitosan but polypyrrole is nearly immiscible with the other two components. Based on the structural characteristics of the membranes, the polypyrrole particles are suggested to be localized at the interface between two phases. Dependence of conductivity of complex membranes on the PPy content. (○) PDLLA/PPy, (▪) PDLLA/ch(10)/PPy, (▵) PDLLA/ch(20)/PPy, (•) PDLLA/ch(30)/PPy, (□) PDLLA/ch(40)/PPy, and (▴) PDLLA/ch(50)-PPy.

Synthesis of Novel Raspberrylike Silica/Polypyrrole Hybrids Based on Single Silica Particle

Novel raspberrylike organic-inorganic hybrids consisting of spherical silica supporting smaller conductive polypyrrole particles were prepared through a self-assembly polymerization process by choosing chitosan as a modifying agent of silica surface. TEM shows the raspberrylike morphology of resulted hybrids. Hydrogen-bonding interaction between the acetylamino of chitosan and hydrogen atom on nitrogen of polypyrrole is a determining parameter to get the raspberrylike morphology. The raspberrylike silica-polypyrrole hybrids exhibited high conductivity of 8 s.cm-1 and its suspensions possessed good stability because of the special surface morphology. In the past few years, organic-inorganic nanocomposite particles have become the subject of rapidly growing interest for their superior properties (optical, mechanical, rheological, electrical, catalytic);1-2 In this field, silica is the most commonly used inorganic support. On the other hand, polypyrrrole(Ppy) is also commonly used organic shell.3 If Ppy nanocomposite systems can be prepared in stable colloidal form, the poor processibility of Ppy can be overcome, at lest partly, so that its applications can extended to wide areas. However, since silica is initially hydrophilic, hydrophobic Ppy shell is very difficult to get by direct surface polymerization. Only “raspberry” like composite was got. A high-resolution TEM picture obtained by Gill et. al. was the first report to reveal this unusual “raspberry” morphology where the composite particles were aggregates of the original small silica particles held together by the conducting polymer component which

Sulphur-polypyrrole composite positive electrode materials for rechargeable lithium batteries

A novel conducting sulphur-polypyrrole composite material was prepared by the chemical polymerization method with sodium p-toluenesulphonate as the dopant, 4-styrenesulphonic sodium salts as the surfactant, and FeCl 3 as the oxidant. The new material was characterized by Raman spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Nanosize polypyrrole particles were uniformly coated onto the surface of the sulphur powder, which significantly improved the electrical conductivity, the capacity and the cycle durability in a lithium cell compared with the bare sulphur electrode.

Synthesis of novel sunflower-like silica/polypyrrole nanocomposites via self-assembly polymerization

Novel sunflower-like organic–inorganic composites consisting of spherical silica and smaller conductive polypyrrole particles were successfully prepared through an in situ self-assembly polymerization process by choosing chitosan as a modifying agent of silica surface. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that on the surface of individual silica particle polypyrrole nanoparticles were anchored perfectly. The sunflower-like silica–polypyrrole composites exhibited conductivity of 8 S cm −1 and colloid stability because of the special surface morphology. Adsorbed chitosan chain may play a dual-role of both providing the active sites for formation of the polypyrrole particles on silica and acting as a stabilizer of the silica–polypyrrole particles. Hydrogen-bonding interaction between the acetylamino group of chitosan and hydrogen atom on nitrogen of polypyrrole is a determining parameter in the former case.

Optical and dielectric properties of polypyrrole nanoparticles in a polyvinylalcohol matrix

We present results of a spectroscopic and dielectric investigation of polypyrrole (PPY) particles dispersed within a polyvinylalcohol (PVA) matrix. These systems, prepared by using a surfactant to encapsulate PPY chains into micelles that were subsequently dispersed in a PVA gel or film, present hybrid electrical characteristics. Their electrical properties are determined by the number, size and state of the aggregation of the micelles, since macroscopic charge transfer must involve charge percolation through the PPY chains followed by hopping between neighboring micelles. We have examined how these properties depend on the relative concentration of the conducting (PPY) and dielectric (PVA) polymers. We suggest that such conducting polymer micelles can be used as efficient trapping vectors for removal of metallic particles of nanoscopic size.

Porous-conductive chitosan scaffolds for tissue engineering II. in vitro and in vivo degradation

Porous-conductive chitosan scaffolds were fabricated by blending conductive polypyrrole (PPy) particles with chitosan solution and employing an improved phase separation method. In vitro and in vivo degradation behaviors of these scaffolds were investigated. In the case of in vitro degradation, an enzymatic degradation system was employed and lysozyme was used as a working enzyme. Meanwhile, the degradation products of scaffolds, glucosamine and N-acetyl-glucosamine, were also analyzed with a HPLC method. In vivo degradation of scaffolds was performed by subcutaneously implanting these scaffolds in rat for pre-scheduled time intervals. In the both cases, the weight-loss of scaffolds was monitored during the whole degradation process for evaluating the degradation of scaffolds. The changes in conductivity of scaffolds afterin vitro or in vivo degradation were also measured using a four-point technique. It was observed that the pore parameters of scaffolds themselves could significantly influence the degradation behaviors of scaffolds but the PPy content in the scaffolds seemed not to impart its effect to the degradation of scaffolds. Degradation dynamics of scaffolds and conductivity measurements indicated that these scaffolds shown fairly different behaviors in their in vitro and in vivo degradation process. According to the results obtained from in vitro and in vivo degradation of scaffolds and based on some requirements of practical tissue engineering application, it was suggested that the PPy content in the scaffold should be slightly higher than 3 wt.% but lower than 6 wt.%.

Physical and electrochemical properties of Nafion/polypyrrole composite membrane for DMFC

Nafion/polypyrrole composite membrane was prepared by chemical in situ polymerization for a direct methanol fuel cell. The composite membrane was characterized by quantitative analysis, DMA, TGA, EPMA, water and methanol uptake tests, conductivity and permeability measurements, and unit cell operation. The mechanical and thermal properties of the composite membrane were enhanced due to the interaction between the polar phase of Nafion and secondary ammonium groups of polypyrrole. In addition, the sorption properties of the composite membrane influenced two transport properties, proton conductivity and methanol crossover. The optimization of cell performance was related to the distribution of polypyrrole particles over the cross section of the membrane. In particular when the polypyrrole particles were mainly present near the surface rather than in the internal space, the difference in the relative proton conductivity and the relative methanol permeability was largest. It is supposed that the existence of the polypyrrole particles near the surface such as thin film was favorable to reducing methanol crossover with maintaining proton conductivity. As a result of that, N/P 003 had higher performance than Nafion under the specific condition.

Singlewall carbon nanotubes covered with polypyrrole nanoparticles by the miniemulsion polymerization

Singlewall carbon nanotubes were covered with polypyrrole via in situ miniemulsion polymerization of pyrrole monomer. They had nanotube surfaces partially enveloped with polypyrrole: the surfaces attached with polypyrrole particles, the surfaces covered with thin polypyrrole film, and bare surfaces. The nanotubes covered with polypyrrole were doped with LiClO 4 and mixed with a binder, Kynar FLEX 2801, to make composite electrode for supercapacitor. The pelletized powder of the composite with Li + ions exhibited higher electrical conductivity and lower percolation threshold concentration than pristine polypyrrole. The composite was used to fabricate the electrode in supercapacitor without adding other conducting material like carbon black. It showed higher specific capacitance than polypyrrole/binder/carbon black composite. This could be explained due to the existence of bare surfaces of SWNTs with high electrical conductivity as well as large surface area.

Percolation study by infrared thermography

AbstractIn two‐phase materials, where the electrical conductivity of the disperse phase is significantly different than that of the host phase, the conductivity versus concentration of the dispersed phase shows percolation behaviour. In order to control the percolation threshold, we prepare a new composite polymer, based on polystyrene (PS) and polypyrrole (PPy) particles, to be used as electromagnetic shielding material. The critical concentration of the percolation was controlled, thus changing the ratio of the size of those particles. In this work, we present a study of the percolation behaviour using infrared thermography stimulated by microwave radiation at 12 GHz and the results are compared with the dc and ac electrical properties. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 335–337, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20816

Glass Transition Temperature Depression at the Percolation Threshold in Carbon Nanotube–Epoxy Resin and Polypyrrole–Epoxy Resin Composites

AbstractSummary: The glass transition temperatures of conducting composites, obtained by blending carbon nanotubes (CNTs) or polypyrrole (PPy) particles with epoxy resin, were investigated by using both differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). For both composites, dc and ac conductivity measurements revealed an electrical percolation threshold at which the glass transition temperature and mechanical modulus of the composites pass through a minimum.DC conductivity, σdc, as a function of the conducting filler concentration of the CNT– (▪) and PPy– (○) epoxy resin composites.magnified imageDC conductivity, σdc, as a function of the conducting filler concentration of the CNT– (▪) and PPy– (○) epoxy resin composites.

Influence of Morphology on the Transport Properties of Perfluorosulfonate Ionomers/Polypyrrole Composite Membrane

Nanosized polypyrrole particles were mainly incorporated into the ionic clusters rather than the nonpolar backbone of Nafion in chemical in-situ polymerization by means of ion−dipole interaction between the sulfonate groups of Nafion and secondary amonium groups of polypyrrole. The incorporation of polypyrrole particles into the clusters, where was the transport pathway, could change the morphology of Nafion matrix, as observed by DSC, SAXS, and WAXD. In particular, the crystallite region of backbones as well as the cluster region of side chains was influenced indirectly by the existence of polypyrrole particles in the ionic clusters. Additionally, the temperature of the cluster transition shifted to a higher value due to the restricted mobility of the clusters, whereas the melting temperature of the nonpolar backbone crystallite shifted to a lower value due to the disruptive effect of swelled cluster. The methanol crossover was reduced more than the proton conductivity because of the existence of polypyr...

Autopolymerization of Pyrrole in the Presence of a Host/Guest Calixarene

Aqueous solutions containing pyrrole and calix-6-arenehexasulfonic acid were found to undergo polymerization in the absence of either a chemical oxidant or electrochemical oxidation. The product was an unstable colloidal suspension consisting of spherical polypyrrole particles measuring ≥500 nm in diameter. Conductivity measurements showed the material to be insulating, while cyclic voltammetry studies demonstrated that it was electroactive. Infrared spectroscopy and microanalysis confirmed that the polypyrrole produced was doped with calix-6-arenehexasulfonic acid. When the reaction was repeated using solutions containing stabilizing agents, stable colloidal dispersions were obtained. These were shown by both particle size analysis and transmission electron microscopy to contain much smaller particles than the unstabilized material, while cyclic voltammetry studies again demonstrated that the polypyrrole obtained was electroactive and sensitive to changes in the surrounding electrolyte.

Interfacial physicochemical properties of functionalized conducting polypyrrole particles

Polypyrrole-coated polystyrene latex particles bearing reactive N-succinimidyl ester functional groups (PS-PPyNSE 75) were prepared by the in situ copolymerization of pyrrole 1 and the active N-succinimidyl ester-functionalized pyrrole 2 (pyrroleNSE), with initial 1: 2 fractions of 25:75 (%) in the presence of sterically stabilized polystyrene (PS) latex particles. PS particles were prepared by dispersion polymerization leading to particles having a diameter of 600±10 nm. The PS-PPyNSE 75 particles were characterized in terms of surface morphology and chemical composition. Surface analysis of the colloidal materials by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) indicated a substantial coating of PS by the reactive conducting copolymer. Infrared spectroscopy permitted to detect pyrroleNSE repeat units at the surface of the particles indicating that 1 and 2 did indeed copolymerise. Reactivity of the PS-PPyNSE 75 particles has been investigated using 2-aminoethanol and 2-mercaptoethanol, two model molecules bearing functional groups borne by proteins. Incubation of the particles with these model molecules clearly showed that the particles are highly reactive towards amine and thiol groups. The functionalized particles were then tested as bioadsorbents. PS-PPyNSE 75 particles were found to be effective in attaching an aminated biotin. The Biotin-decorated PS-PPyNSE 75 latex particles were incubated with avidin with a result of a significant change in the surface composition that is in line with the attachment of the protein by specific binding to biotin.

Porous-conductive chitosan scaffolds for tissue engineering, 1. Preparation and characterization.

Novel porous-conductive chitosan scaffolds were fabricated by incorporating conductive polypyrrole (PPy) particles into a chitosan matrix and employing a phase separation technique to build pores inside the scaffolds. Conductive polypyrrole particles were prepared with a microemulsion method using FeCl3 as a dopant. The preparation conditions were optimized to obtain scaffolds with controlled pore size and porosity. The conductivity of the scaffolds was investigated using a standard four-point probe technique. It was found that several kinds of scaffolds showed a conductivity close to 10(-3) S.cm(-1) with a low polypyrrole loading of around 2 wt.-%. The main mechanical properties, such as tensile strength, breaking elongation and Young's modulus of the scaffolds, were examined both in the dry and in the hydrated states. The results indicated that a few different kinds of scaffolds exhibited the desired mechanical strength for some tissue engineering applications. The miscibility of polypyrrole and chitosan was also evaluated using a dynamic mechanical method. The presence of significant phase separation was detected in non-porous PPy/chitosan scaffolds but enhanced miscibility in porous PPy/chitosan scaffolds was observed.

XPS study of the adsorption mechanisms of DNA onto polypyrrole particles

DNA adsorption onto polypyrrole (PPy) powder particles has been monitored, ex situ, by X‐ray photoelectron spectroscopy (XPS) technique. DNA adsorption isotherms were determined by the quantitative analysis of the XPS spectra, and by plotting the X/N atomic ratios (X = C, O, Cl, P and Na) versus DNA equilibrium concentration. All XPS isotherms are of high affinity type, showing high adsorption amounts at low DNA concentrations in the suspension. Moreover, inspection of the C1s peak structure of the PPy–DNA complex revealed that it gradually gets wider and less tailing as DNA adsorbs, clearly showing the DNA contribution to the peak enlargement. In addition, the changes observed in the Cl2p structure bring a strong supporting evidence of anion‐exchange mechanism that takes place at initial stages of the interaction. Actually, the polypyrrole backbone loses part of its residual chlorides as the first DNA fragments adsorb and neutralize the PPy positive charges at the interface. Moreover, at relatively high amounts of adsorbed DNA, the PPy surface becomes screened necessitating thus that sodium cations co‐adsorb in order to compensate for the excess of DNA negative charges. As a consequence of such screening of the PPy surface, DNA adsorption results in a positive spectral shift of all peaks of approximately 2.0 eV, a value that leads to the conclusion that DNA partially covers the PPy.

Structural and Magnetic Properties of Polypyrrole Nanocomposites

We report the synthesis and characterization of conducting polymer nanocomposites based on polypyrrole(PPY)and Fe2O3magnetic particles. The global structure of PPY nanocomposites was obtained by X-ray Diffraction(XRD)method using a new approximation based on Generalized Fermi Function. The local structural parameters of Fe sites in Fe2O3nanocrystallites embedded in PPY were determined by X-ray Absorption Spectroscopy(EXAFS). The lack of hysteresis loop for the magnetization curves of the composite PPY-Fe2O3indicates a superparamagnetic behavior which is typical for nanosized magnetic particles.

Synthesis, characterization and biomedical applications of functionalized polypyrrole‐coated polystyrene latex particles

AbstractN‐hydroxysuccinimide‐functionalized polypyrrole (PPy–NHS) coated onto polystyrene (PS) latex particles were prepared by the in situ copolymerization of pyrrole and the active ester‐functionalized pyrrole (pyrrole–NHS) in the presence of bare PS substrates. The initial comonomer concentration ratios were 25/75 and 50/50 for pyrrole and pyrrole–NHS, respectively. PS particles were prepared by two methods: emulsion polymerization, leading to particle sizes in the 450–500 nm range, and dispersion polymerization using poly(N‐vinylpyrrolidone) (PNVP) as a steric stabilizer. The polypyrrole‐coated PS particles (PS–PPy) were characterized in terms of particle size, surface charge and surface chemical composition. For the “emulsion” PS coated with polypyrrole, the particles were evaluated as bioadsorbents of human serum albumin (HSA). It is believed that the proteins attach themselves by covalent bonds at the surfaces of NHS‐functionalized PPy–PS particles. It is shown that the maximum adsorption levels off at 0.2 mg/m2 in the case of the 50/50 initial ratio concentration but only to 0.02 mg/m2 in the case of the 25/75 ratio, an indication that a higher concentration of surface reactive groups hamper the covalent attachment of HSA at the surfaces of polypyrrole particles. Copyright © 2003 John Wiley & Sons, Ltd.