Characteristics Of Polypyrrole Research Articles

Fabrication of polypyrrole gas sensor for detection of NH3 using an oxidizing agent and pyrrole combinations: Studies and characterizations

The organic polymer known as Polypyrrole (Ppy) is synthesized when pyrrole monomers are polymerized. Excellent thermal stability, superior electrical conductivity, and environmental stability are all characteristics of Polypyrrole. Chemical oxidative polymerization was used to synthesize Ppy using Ferric chloride (FeCl3) as an oxidizing agent and surfactant CTAB in aqueous solution. Oxidant (FeCl3) to pyrrole varied in different molar ratios (2, 3, 4 and 5). It was found that increasing this ratio up to 4 increases PPy's conductivity. XRD, FTIR, and SEM were used to characterize Ppy. The conductive nature of Ppy was studied by I–V characteristics. The best conductive polymer is studied for the NH3 gas response.

Effect of anionic dopants on thickness, morphology and electrical properties of polypyrrole ultra-thin films prepared by in situ chemical polymerization

Abstract The effect of different dopant anions on deposition and characteristics of polypyrrole (PPy) thin film has been studied in this work. Ultra-thin films of conducting PPy were deposited on insulating surfaces of glass and oxidized silicon wafer by in situ chemical polymerization in the presence of different anionic dopants including sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, α-naphthalene sulfonic acid, anthraquinone-2-sulfonic acid sodium salt monohydrate/5-sulfosalicylic acid dehydrate, and camphor sulfonic acid. Hydrophilic/hydrophobic properties and morphology of the self-assembled monolayer of N-(3-trimethoxysilylpropyl)pyrrole, the surface modifying agent in this work, and PPy thin films were characterized before and after deposition by contact angle measurements, field emission scanning electron microscopy, and atomic force microscopy. Chemical structure, thickness, and conductivity of the thin films were also studied by attenuated total reflectance Fourier transform infrared spectrometer, ellipsometry, and four-point probe measurements. The results showed deposition of thin films of conducting PPy with comparable thickness in the range of 6–31 nm and different morphologies, uniformity, and smoothness with average roughness in the range of 0.3–6 nm and relatively high range of conductivity on the modified surfaces.

Direct pyrolysis mass spectrometry to investigate the effects of dopants on characteristics of polypyrrole and its copolymers

Polypyrrole and its copolymers with terepthalic acid bis-(2-thiophen-3-yl-ethyl)ester, (P(TATE-co-Py) were characterized by direct pyrolysis mass spectrometry to investigate the effects of dopant on thermal stability and conductivity. Conductivities of the films were measured with four-probe technique, and the results were compared with the pyrolysis data. In general, an increase in conductivity was detected as the stability of dopant increased. The extent of doping and the strength of interaction between the dopant and the polymer were decreased upon copolymerization with terepthalic acid bis-(2-thiophen-3-yl-ethyl)ester.

Synthesis and Structural and Electrical Characteristics of Polypyrrole Nanotube/TiO2 Hybrid Composites

Hybrid composites of conducting polypyrrole nanotubes with TiO2 nanoparticles were synthesized in the presence of β-naphthalenesulfonic acid by chemical oxidative polymerization. The morphology, structure, and electrical properties were investigated by several experimental techniques. The results indicated that the structural and electrical properties of the composites were influenced by the content of TiO2 nanoparticles. The DC conductivity of the composites increased by one order of magnitude when the concentration of TiO2 was 0.1 M compared with pure PPy nanotubes. AC conductivity of the composites showed the similar trend with the TiO2 content and obeyed the power law index in the 101–107 Hz range. The electrorheological properties of the composite under steady and oscillatory shear were also evaluated.

Series resistance determination of Au/Polypyrrole/p-Si/Al structure by current–voltage measurements at low temperatures

The current–voltage ( I–V) characteristics of Polypyrrole(PPy)/p-Si/Al structure have been investigated as a function of temperature. A modified Norde function combined with conventional forward I–V method has been used to extract the junction parameters including the ideality factor, barrier height and series resistance. Norde function has been compared with the Cheung functions and it has been seen that there is a good agreement with both method for the barrier height values. However, the values of series resistance have very different especially towards to the lower temperatures. This is attributed to non-ideal I–V characteristics of the Au/PPy/p-Si/Al structure and non-pure Thermionic emission theory due to the low temperature effects.

Electrochemical polymerization of polypyrrole (PPy) and poly(3-hexylthiophene) (P3HT) using functionalized single-wall carbon nanotubes

We report on the synthesis and characteristics of polypyrrole (PPy) nanowires and poly(3-hexylthiophene) (P3HT) films by using functionalized single-wall carbon nanotubes (F-SWCNTs). The F-SWCNTs were prepared by the process of ultrasonication of SWCNTs mixture with nitric and sulfuric acid (3:1 volume ratio) solution. The F-SWCNTs has the pending carboxylic acid group (COOH). The PPy nanowires and bulky P3HT film were electrochemically polymerized based on the Al2O3 nanoporous template and on the ITO glass, respectively, by using the F-SWCNTs as a dopant in electrolyte. We compared the structural characteristics between the arc-grown SWCNTs and the F-SWCNTs through a scanning electron microscope (SEM), a Fourier transform infrared (FT-IR) spectroscope, a Raman spectroscope, an X-ray photoelectron spectroscope, and an elemental analysis. The formation of PPy nanowires and bulky P3HT film were confirmed through SEM and FT-IR experiments.

Improved cathodic expansions of polypyrrole films by poly(2-methoxyaniline-5-sulfonate) incorporation

We describe the effect of conducting guest polymer, poly(2-methoxyaniline-5-sulfonate, PMAS), incorporation on the electrochemomechanical deforming (ECMD) characteristics of polypyrrole (PPy) film. The films electrodeposited in the aqueous solutions having dodecylbenzene sulfonate (DBS) as the main supporting electrolyte mixed with various amounts of PMAS as the polymer additive, exhibited the drastic change of ECMD behaviors as a function of PMAS content. A complicated ECMD behavior was observed for the PPy film having 5% PMAS dopant in 0.5 M KCl/aqueous solution, which turned to be a simple cathodic expansion (4.5% in strain) in 0.5 M tetra-bulyammonium tetra-fluoroborate/acetonitrile(AcCN) solution. The large cathodic expansion of 6.2% was observed in tetra-bulyammonium chloride/AcCN solution. Responses of ECMD behaviors of the films in Square-Wave Voltammetry (SWV) elucidate that the anion exchange is simultaneously occurred with cation exchange even in the cathodic expansive films. For the cathodic expansion of PPy film, the PMAS incorporation is effective to improve the deformation magnitude. The cathodic expansion should be improved in the judicious selection of electrolyte having bulky cation with small anion as well as preferable solvent.

Characteristics of polypyrrole (PPy) nano-tubules made by templated ac electropolymerization

Electrochemical alternating current (ac) method designed for the synthesis of polypyrrole (PPy) nano-tubule arrays is the topic of this paper. Two-step anodic aluminum oxide (AAO) membrane is used as a template. The morphology of PPy nano-tubules is observed by SEM and discussed. FTIR spectra exhibit that the peaks of PPy nano-tubules shift compared to conventional PPy film.

OXIDANT EFFECTS ON POLYPYRROLE AND POLYANILINE SENSOR FOR SEVERAL VOLATILE ORGANIC GASES

The properties of polypyrrole and polyaniline sensor made from chemical polymerization were investigated. It was found that the oxidant (ammonium persulfate) affected solubility, conductivity and the sensing characteristics of polypyrrole and polyaniline. Atomic force microscopy (AFM) was used to investigate the morphology of the sensing films. A sensor array with 6 sensors was developed to recognize various kinds and quantities of volatile organic compounds (VOCs), such as benzene, toluene and chloroform. Principal Components Analysis (PCA) was used to analyze the VOC sensing characteristics.

Effect of Dopants on Characteristics of Polypyrrole as a Liquid Crystal Alignment Layer

Electrochemically polymerized polypyrrole (PPy) films with different dopants showed different surface energies. The films were used as alignment layers of liquid crystal displays (LCDs). The PPy films doped with ClO4 − (PPy/ClO4) and PF6 − (PPy/PF6) showed surface energies of 43.2 and 32.3 mJ/m2, respectively, while the pretilt angles of 4-cyano-4′-pentylbiphenyl on the films were 5.6 ± 0.3 and 14.0 ± 2.2 degrees, respectively. The electro-optic response time measured by light transmittance through the twisted nematic(TN) LCDs on switch-on was shorter for the display with PPy/PF6 than for that with PPy/ClO4. However, the turn-off response time was shorter for the display with PPy/ClO4 than for that with PPy/PF6. The total response time, which is the sum of the turn-on and turn-off response times, was 75 and 120 msec at 3.0 V pp for the displays with PPy/ClO4 and PPy/PF6, respectively.

Effect of Electrolytes on Redox Reactivity of Polypyrrole

Doping and dedoping characteristics of polypyrrole (PPy) formed electrochemically have been examined by means of energy-dispersive X-ray spectroscopy (EDS). Dodecylsulfate ions (DS−) and perchlorate ions (ClO−4) were embedded simultaneously in PPy when both ions were present on the polymerization of pyrrole. Sequential formation of PPy in the single dopant system allowed PPy/ClO4 to grow in the bulk of PPy/DS but not vice versa. DS− was embedded not to leave the polymer on reduction but ClO−4 moved in and out of the polymer on redox reaction. Cyclic voltammetry was employed to determine the redox reactivity of PPy in different electrolyte systems. NaClO4 was a better electrolyte for cyclic redox reaction than LiClO4 or KClO4. NaCl was a good electrolyte for cyclic redox reaction but Cl− failed to penetrate in the PPy/DS bulk on reoxidation. The cyclic redox reactivity lasted longest when PPy/DS was redox-cycled sequentially in the NaCl electrolyte system and then in the NaClO4 system. © 1997 John Wiley & Sons, Ltd.

Chemical modification of polypyrrole. II. Thermal stability, dielectric, and conductivity characteristics of polypyrrole substituted with phthalic and pyromellitic dianhydride

AbstractPolypyrrole (PPY) was electrophilically polycondensed with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA). PPY–PA and PPY–PMDA polycondensates were evaluated in regard to their thermal stability and dielectric and conductivity behavior. The overall thermal stability is in the order PPY < PPY–PA < PPY–PMDA, which may be rationalized in terms of intra‐ and intermolecularly cross‐linked structures of the polycondensates. IR spectral analyses of PPY–PA and PPY–PMDA subjected to heating at 300, 400, 500, and 550°C, respectively, were conducted to understand some of the structural changes in the polymer matrices. Both PPY–PA and PPY–PMDA exhibit high dielectric constants (200 and 125) at low frequency (103 Hz), which fall monotonically with increasing frequency, suggesting the possibility of interfacial polarization. The conductivity values of PPY–PA and PPY–PMDA are in the range 10−3–10−4 ohm−1 cm−1, which are conspicuously lower than that for unmodified PPY (2.5). This is due to the adverse effect of incresing temperature on the PPY chain stability, whereby structural conjugation and eventually conductivity will be affected. © 1994 John Wiley & Sons, Inc.