Polypyrrole Composite Films Research Articles

Polymerization of pyrrole derivatives on polyacrylonitrile matrix, FTIR–ATR and dielectric spectroscopic characterization of composite thin films

Oxidative polymerization of acrylonitrile (AN) initiated by Ce(IV)–oxalic acid redox system in the aqueous medium was performed and polyacrylonitrile (PAN)/polypyrrole (PPy) composite thin films were prepared by polymerization of pyrrole on polyacrylonitrile matrix. Effect of concentration of pyrrole derivatives on the resulting polymeric film properties was investigated. The influence of the pyrrole derivative type and content on the dielectric permittivity, dielectric loss and electrical properties of the composite films were analyzed in the frequency range from 0.05 Hz to 10 MHz. For a selected concentration of 200 μl of composite films at 10 7 Hz, the conductivity was found to be in the following order: PAN–PPy < PAN–PNMPy < PAN–PNPhPy. Dielectric constant increase of the composite films was more obvious when the quantity of n-phenyl pyrrole was increased. A linear relationship was observed between the absorbances (FTIR–ATR) and conductivities (dielectric spectroscopy).

Newly synthesized poly(glycidyl methacrylate-co-3-thienylmethylmethacrylate)-based electrode designs for phenol biosensors

A newly synthesized poly(glycidyl methacrylate-co-3-thienylmethylmethacrylate) [poly(GMA-co-MTM)] was designed to fabricate various HRP electrodes for detection of phenol derivatives. The results showed that the poly(GMA-co-MTM)/polypyrrole composite film microarchitecture provided a good electroactivity as a result of pyrrole and thiophene interaction, and provided chemical bonds for enzyme immobilization via the epoxy groups of poly(GMA-co-MTM). The glassy carbon-based working electrode displayed significantly higher performance for the same composite film configuration comparing to the gold-based working electrode. Poly(GMA-co-MTM)/polypyrrole/HRP coated glassy carbon electrode exhibited a fast response less than 3s, a high sensitivity (200 nA microM(-1)for hydroquinone), a good operational stability (%RSD values ranged between 2 and 5.1 for all phenolics), a long-term stability (retained about 80% of initial activity at the end of 40th day) and a low detection limit ranging between 0.13 and 1.87 microM for the tested.

Highly sensitive humidity sensor at low humidity based on the quaternized polypyrrole composite film

Polypyrrole composite was fabricated by using chemical polymerization at room temperature, which was further quaternized with 1,4-bromobutane to prepare the humidity sensitive material. The electrical properties of the sensor were measured. The results showed that the quaternized polypyrrole composite film exhibited low impedance at very low humidity; the impedance value was about 780 kΩ at 11% RH and the impedance changed from 10 6 to 10 3 Ω between 11% and 95% RH, which was suitable for detection of low humidity. Moreover, the logarithm of impedance of the polypyrrole composite film varied linearly ( R 2 = 0.9916) with relative humidity in the range of 11–95% RH. Surface and cross-sectional morphology of the films, response–recovery time and hysteresis were also measured and estimated. The sensing mechanism of the sensor was also investigated.

Characterization of electrodeposited polymeric and composite modified electrodes on cobalt based alloy

Using the electrochemical oxidation of monomers: pyrrole, aniline and pyrrole—aniline mixture of different compositions in aqueous solutions containing dopant anions as supporting electrolyte, the polymeric conductive films of polypyrrole and polyaniline and also, the composite films of polypyrrole—polyaniline were electrodeposited on the Co67Cr29W4 alloy electrode surface. The electrochemical properties of the obtained modified electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that the mechanism of the redox process is complex and may be governed by the diffusion of the electrolyte. It was observed that the cobalt based alloy substrate had a considerable effect on the electrochemical activity of the polypyrrole and polyaniline films and that because in the presence of polymeric film, anodization of these modified electrodes resulted in formation of an oxides complex film and polymeric layers simultaneously. This is consistent with a galvanic interaction between the polymer and the cobalt–chromium based alloy substrate, giving rise to oxidation of cobalt, chromium and tungsten and reduction of the polymer.

Physical, optical, and electrical properties of a new conducting polymer

This work studies the electrical and optical properties of the conducting polymer composite films of polypyrrole–chitosan (PPy–CHI). The surface plasmon resonance (SPR) technique was used to study the optical properties of PPy and PPy–CHI composite films. Then, the values of the real and imaginary parts of the refractive indexes of PPy and PPy–CHI films were obtained by nonlinear least square fitting using Fresnel equations for a three-layer system of SPR system. The electrical conductivity measurements showed that the conductivity of the electrochemical prepared films improved in the presence of CHI and can be controlled by varying the CHI amount in the composite. The thermal diffusivity of the PPy–CHI composite films was measured by open photoacoustic spectroscopy and it has been shown that the thermal diffusivity is related to the electron migration in the conjugation chain length. The increase in electromagnetic interference shielding effectiveness (EMI SE) with the increase in electrical conductivity of the films is mostly from shielding by reflection rather than absorption.

Comparative study of Fe 2+/H 2O 2 and Fe 3+/H 2O 2 electro-oxidation systems in the degradation of amaranth using anthraquinone/polypyrrole composite film modified graphite cathode

Removal of amaranth from aqueous solutions by Fe 2+/H 2O 2 and Fe 3+/H 2O 2 electro-oxidation systems was comparatively studied in an undivided electrochemical cell with anthraquinonedisulfonate (AQDS)/polypyrrole (PPy) composite film modified graphite as cathode. The modified cathode allowed the formation of strong oxidant hydroxyl radical ( OH) in the medium via Fenton’s reaction between cathodically generated H 2O 2 and added or regenerated Fe 2+. The effects of solution pH and iron catalyst concentration on dye degradation by the two systems were studied and compared. Degradation intermediates were analyzed by FTIR and GC–MS, and a tentative reaction pathway is proposed. Dye decay reaction always obeys pseudo-first-order kinetics for Fe 3+/H 2O 2 process, while dye degradation follows a two-stage process with each stage obeying pseudo-first-order kinetics in the case of Fe 2+/H 2O 2 system. In addition, the long-term stability and structural relaxation of the composite film during multiple experimental runs are also examined.

Synthesis and Electrical Characterization of Self-Supported Conducting Polypyrrole-Poly(vinylidene fluoride) Composite Films

We report the synthesis of polypyrrole composite films by chemical oxidation polymerization of pyrrole dif- fused inside poly(vinylidene fluoride) matrix and temperature dependant dc conductivity study of these composite films. Ammonium persulfate is used as an oxidizing agent and HCl as the dopant in aqueous medium. This technique produces highly conductive, flexible and free standing polymer composite films in semi-interpenetrating architecture. It is observed that conductivity of the composite films can be controlled by varying the dopant concentration. The variation of conduc- tivity with temperature indicates the semiconducting nature of these composite films. The temperature dependence of conductivity is explained in the light of two different models from which activation energy (Ea) and other hopping pa- rameters are determined. Experimental data fits well with variable range hopping model and three dimensional charge transport mechanism is shown to occur in these films.

Black Layers on Aluminum Substrate – Evaluation of Corrosion Behavior

The paper presents some preliminary experimental results dealing with electrochemical synthesis and corrosion behavior of various black layers types onto Al substrates, suitable to be used as selective absorber coatings in the case of thermal energy production from solar energy, involving several different procedures, respectively: (i) electrodeposition of black Ni-Mo alloy after an initial anodizing in nitric acid electrolyte that offers a very good adherence of the further applied coatings; (ii) cathodic deposition of black Mo based layers after an initial double zincating procedure; (iii) black coatings through a.c. electrochemical coloring of aluminum anodic oxides, using AgNO3/H2SO4, NiSO4 based solutions; (iv) black composite polypyrrole films. The obtained black layers are characterized by a good throwing power, homogeneity, smoothness and adherence, as shown by SEM and AFM investigations. Also, they present a good solar absorption and low values of infrared emittance. To evaluate the resistance of black coating layers against corrosion, several accelerated corrosion tests have been performed, respectively: (i) continuous immersion in 0.5M NaCl for 408 hours with intermediary visual examinations and recording of corrosion potential; (ii) potentiodynamic polarization curves in 0.5M NaCl; (iii) impedance spectra in 0.5M NaCl at open circuit potential using a Zahner IM6e potentiostatic equipment. The corrosion performances are discussed taking into account the applied preparation procedures.

Thin black layers on aluminum substrate—electrochemical synthesis and characterization

AbstractThe article presents some preliminary experimental results dealing with electrochemical synthesis and morphological, optical characterization of various types of black layers onto Al substrates, involving both inorganic metallic salts of nickel, molybdenum, and conducting polymers, respectively, polypyrrole layers. The article discusses a new procedure for direct electrodeposition of black Ni, black layers based on Mo compounds during a cathodic process as well as black composite polypyrrole films during anodic oxidation that involves an initial anodizing in nitric acid electrolyte that proved to offer a very good adherence of the metal then plated on Al surfaces. Al surface morphology evolution against applied c.d. and duration during initial anodizing was also investigated, by SEM technique. The obtained black layers are characterized by a good throwing power, homogeneity, smoothness, and adherence. Also, black layers formed by a.c. electrochemical coloring in Ag‐ and Ni‐based solutions are discussed. Optical characterization has been also performed to evaluate their solar absorptance and thermal emittance coefficients and a comparative evaluation is presented. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Properties of Dendrimer‐Encapsulated Pt Nanoparticles Doped Polypyrrole Composite Films and Their Electrocatalytic Activity for Glucose Oxidation

AbstractA type of novel electroanalytical sensing nanobiocomposite material was prepared by electropolymerization of pyrrole containing poly(amidoamine) dendrimers‐encapsulated platinum nanoparticles (Pt‐PAMAM), and glucose oxidase (GOx). The Pt nanoparticles encapsulated in PAMAM are nearly monodisperse with an average diameter of 3 nm, and they provide electrical conductivity. Polypyrrole acts as a polymer backbone to give stable and homogeneous cast thin films, and it also defines the electrical conductivity. Both Polypyrrole and PAMAM can provide a favorable microenvironment to keep the bioactivity of enzymes such as glucose oxidase. The homogeneity of GOx/Pt‐PAMAM‐PPy nanobiocomposite films was characterized by atomic force microscopy (AFM). Amperometric biosensors fabricated with these materials were characterized electrochemically using cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and amperometric measurements in the presence of hydrogen peroxide or glucose. All those show the resultant biosensor sensitivity was strongly enhanced within the nanobiocomposite film. The optimized glucose biosensor displayed a sensitivity of 164 μA mM−1 cm−1, a linear range of 0.2 to 600 μM, a detection limit of 10 nM, and a response time of &lt;3 s.

Gas sensing behavior of nano-structured polypyrrole prepared by “carbon nanotubes seeding” approach

Gas-sensing behaviors to chemical vapors of both the polypyrrole and the nano-structured polypyrrole composite film prepared by adding a small amount of carbon nano-tubes (CNTs) to act as nano-fiber seeds were investigated. The experimental results showed that although the gas-sensitivity of the film to trimethylamine was decreased to a certain extent by adding CNTs to form the nano-structure, the resistance of the film to moisture was improved greatly while the rapid response was remained. Moreover, SEM and XRD indicated that the orientation degree of the polypyrrole composite film was improved significantly by the CNTs.

Force detection with Donnan equilibrium in polypyrrole film

Mechanical stimuli to polypyrrole (PPy) composite film could be detected as a spike-wise current by applying or releasing a stepwise tensioning-load in electrochemical cell. The current polarity observed here varies with the film preparation. A negative current was observed in the PPy film electrodeposited in dodecylbenzene sulfonic acid (PPyDBS), besides a positive current was observed in the film electrodeposited in bis(trifluoromethane sulfonyl)imide (PPyTFSI) with applying a load. Reversal currents were observed with releasing a load from the films. Switching of the polarity of the induced current well corresponded to the film actuation polarity, indicating that the current induction is the phenomenological counterpart of the electrochemical actuation. Perturbation of Donnan equilibrium by external pressure possibly generates an ion flux across the film/electrolyte interface, resulting in (dis)charge of the PPy similar to the redox process.

Preparation and characterization of Ppy/Al 2O 3/Al used as solid-state capacitors for microsystems—Effect of amount of electricity passed

This investigation focuses on the preparation of polypyrrole composite films, Ppy/Al 2O 3/Al, used as solid-state capacitor with electrochemical polymerization in the presence of DBSA, co-dopant and co-solvent. The parameters of the solid-state capacitor, i.e. leakage current (Lc), capacitor (Cs), dicipation factor (DF) and equivalent series resistance (ESR), were measured in this study. The surface morphology and compositions of the prepared Ppy/Al 2O 3/Al electrolyte were examined using SEM and EDS, respectively. Further, for 3 C of electricity passed, the values of Lc, Cs, DF and ESR of the Ppy/Al 2O 3/Al capacitor prepared with 2-NSNa and DBSA as a co-dopant were measured to be 0.029 ± 0.005 μA cm −2, 688.8 ± 8.28 nF cm −2, 14.35 ± 5.63% and 18.63 ± 3.48 Ω. Further, the parameters both of R ox and R ppy are 135.5 and 7.047 Ω.

Examining the use of Fe3O4 nanoparticles to enhance the NH3 sensitivity of polypyrrole films

Polypyrrole (PPy) composite films with different contents of Fe3O4 were prepared by in-situ polymerization of pyrrole in aqueous solutions. The dependence of dc current changes on the response of the samples exposure to NH3 vapor has been investigated. The results shows the composite films are more stable than the pristine ones after being exposed to NH3 vapor. Meanwhile, the response time was reduced with increasing the Fe3O4 content in the films. The results might be originated from the structural changes in the PPy films caused by the addition of Fe3O4.

Anion and cation transport in composite films of polypyrrole with a sulphonated silica (ormosil) hydrogel

Composite films of polypyrrole with a sulphonated organically modified silica (ormosil) have been prepared on electrodes by the electrochemical oxidation of pyrrole in a liquid sol–gel electrolyte. The ormosil is incorporated into the polypyrrole matrix as an immobile polymeric counterion in addition to mobile Cl − counterions from the sol–gel electrolyte. Ion transport in the composites was investigated by impedance spectroscopy and electron microprobe analysis. The presence of both mobile and immobile counterions allows potential control of the mode of ion transport, with anion transport dominating at high potentials and cation transport dominating at low potentials. As the polymer is un-doped (reduced), its ionic conductivity first decreases as mobile anions are expelled, and then increases as cations and excess electrolyte are incorporated.

A Selective Cholesterol Biosensor Based on Composite Film Modified Electrode for Amperometric Detection

An amperometric cholesterol biosensor based on immobilization of cholesterol oxidase in a Prussian blue (PB)/polypyrrole (PPy) composite film on the surface of a glassy carbon electrode was fabricated. Hydrogen peroxide produced by the enzymatic reaction was catalytically reduced on the PB film electrode at 0 V with a sensitivity of 39 μA (mol/L)−1. Cholesterol in the concentration range of 10−5 ˜ 10−4 mol/L was determined with a detection limit of 6 × 10−7 mol/L by amperometric method. Normal coexisting compounds in the bio-samples such as ascorbic acid and uric acid do not interfere with the determination. The excellent properties of the sensor in sensitivity and selectivity are attributed to the PB/PPy layer modified on the sensor.

Electrochemical actuator based on monolithic polypyrrole–TiO2 nanoparticle composite film

A polypyrrole (PPy) composite film with a pure PPy zone and a PPy–TiO2 nanoparticle composite zone in its cross-sectional direction was synthesized by direct oxidation of pyrrole successively in an electrolyte with or without TiO2 nanoparticles. The volume content of TiO2 in the composite film was tested to be lower than 0.9%. The actuator fabricated from this monolithic PPy film bends uniformly in two directions with a maximum bending angle larger than 90° and has a high response rate (∼115°s−1 at 1.0V versus SCE) and a long lifetime (>20,000 cycles) in a 1M LiClO4 aqueous solution. The high performance of this actuator resulted from the non-delamination and intrinsic asymmetric structure and the high conductivity of PPy film.

Soft Actuators based on Polypyrrole and Polyaniline Composite Films

ABSTRACTElongation and contraction of polypyrrole and poly(3-methoxyaniline-5-sulfonate) (PMAS) composite films induced upon electrochemical oxidation and reduction, viz., electrochemomechanical deformation (ECMD) are studied. The composite films were electrochemically prepared in electrolyte solutions of pyrrole and dodecylbenzene sulfonic (DBS) acid with a presence of PMAS acid. The contents of DBS and PMAS were varied. Films which were obtained at higher contents of PMAS, were gel like due to a lot of water content. The change of film length due to ECMD was measured as functions of various electrolytes in either aqueous or organic solvents. The results indicated that films exhibited both cathodic and anodic expansions depending on the bulkiness of cations and anions as well as the content of PMAS.

Electronic properties of polyamide–PPy/metal junction and electrical conductivity of a typical sample at low temperatures

Electronic properties of junctions fabricated by polyamide–polypyrrole composite films polymerized with adjusted doping concentration and various metal contacts (In, Al, Au and Ag) were investigated. For the junctions giving good rectification I 0, n and φ b were specified. Conductivity of polyamide–polypyrrole composite polymer was obtained as a function of temperature in the 70–320 K range and was found to obey the VRH model. In addition the Mott parameters were evaluated.

Film Resonance on Acoustic Wave Devices: The Roles of Frequency and Contacting Fluid

The dynamics of composite films of polypyrrole and sodium poly(styrenesulfonate) were studied by means of the electrochemical quartz crystal microbalance. Admittance spectra recorded after successive cycles of electrodeposition showed dramatic changes, which were interpreted in terms of acoustic resonance of the film. Reports of this phenomenon are rare and unquantified, presenting a unique opportunity for the first test of a recently reported theoretical model. The model, valid at frequencies in the vicinity of film resonance, is represented in terms of an equivalent electrical circuit with parallel LCR elements in the motional arm of the resonator. Since it was developed for viscoelastic films exposed to a vacuum, this provides an opportunity to test the importance of the fluid necessarily present in in situ electrochemical experiments. Measurements at the fundamental frequency and at higher harmonics reveal the sensitivity of film resonance effects to frequency and provide insights into film dynamics through the variation of shear moduli with time scale (frequency).