Chemical Oxidation Of Pyrrole Research Articles

In-Situ Coating of Iron with a Conducting Polymer, Polypyrrole, as a Promise for Corrosion Protection

Iron microparticles were coated with polypyrrole in situ during the chemical oxidation of pyrrole with ammonium peroxydisulfate in aqueous medium. A series of hybrid organic/inorganic core–shell materials were prepared with 30–76 wt% iron content. Polypyrrole coating was revealed by scanning electron microscopy, and its molecular structure and completeness were proved by FTIR and Raman spectroscopies. The composites of polypyrrole/carbonyl iron were obtained as powders and characterized with respect to their electrical properties. Their resistivity was monitored by the four-point van der Pauw method under 0.01–10 MPa pressure. In an apparent paradox, the resistivity of composites increased from the units Ω cm for neat polypyrrole to thousands Ω cm for the highest iron content despite the high conductivity of iron. This means that composite conductivity is controlled by the electrical properties of the polypyrrole matrix. The change of sample size during the compression was also recorded and provides a parameter reflecting the mechanical properties of composites. In addition to conductivity, the composites displayed magnetic properties afforded by the presence of iron. The study also illustrates the feasibility of the polypyrrole coating on macroscopic objects, demonstrated by an iron nail, and offers potential application in the corrosion protection of iron. The differences in the morphology of micro- and macroscopic polypyrrole objects are described.

Aqueous Processable One-Dimensional Polypyrrole Nanostructured by Lignocellulose Nanofibril: A Conductive Interfacing Biomaterial.

One-dimensional (1D) nanomaterials of conductive polypyrrole (PPy) are competitive biomaterials for constructing bioelectronics to interface with biological systems. Synergistic synthesis using lignocellulose nanofibrils (LCNF) as a structural template in chemical oxidation of pyrrole with Fe(III) ions facilitates surface-confined polymerization of pyrrole on the nanofibril surface within a submicrometer- and micrometer-scale fibril length. It yields a core-shell nanocomposite of PPy@LCNF, wherein the surface of each individual fibril is coated with a thin nanoscale layer of PPy. A highly positive surface charge originating from protonated PPy gives this 1D nanomaterial a durable aqueous dispersity. The fibril-fibril entanglement in the PPy@LCNFs facilely supported versatile downstream processing, e.g., spray thin-coating on glass, flexible membranes with robust mechanics, or three-dimensional cryogels. A high electrical conductivity in the magnitude of several to 12 S·cm-1 was confirmed for the solid-form PPy@LCNFs. The PPy@LCNFs are electroactive and show potential cycling capacity, encompassing a large capacitance. Dynamic control of the doping/undoping process by applying an electric field combines electronic and ionic conductivity through the PPy@LCNFs. The low cytotoxicity of the material is confirmed in noncontact cell culture of human dermal fibroblasts. This study underpins the promises for this nanocomposite PPy@LCNF as a smart platform nanomaterial in constructing interfacing bioelectronics.

Polypyrrole/zeolite composite – A nanoadsorbent for reactive dyes removal from synthetic solution

Synthetic dyes are among the common pollutants in the ecosystem. In the present study, polypyrrole/zeolite (PPy/Ze) nanocomposite was prepared and subsequently assessed for the removal of Reactive blue (RB) and Reactive red (RR) from synthetic solution. The polymeric PPy/Ze composite was synthesized by chemical oxidation of pyrrole in the presence of zeolite. Electron microscopic images (transmission and scanning) indicate that PPy/Ze nanocomposite was spherical in shape with an average size of 40–80 nm. The characteristic pyrrole and zeolite Fourier transform infrared spectrum peaks (1542 cm−1, 1463 cm−1, 1156 cm−1, 1054 cm−1, 879 cm−1 and 756 cm−1) in the nanocomposite confirmed zeolite integration with polypyrrole. Experimental variables such as PPy/Ze nanocomposite dose, initial RB and RR concentration, reaction temperature and pH were optimized. The PPy/Ze nanocomposite adsorbed 86.2% of RB and 88.3% of RR from synthetic solution at optimal conditions (pH 9, initial RR or RB concentration, 75 mg/l; PPy/Ze dose, 1.8 g/l; and temperature, 50 °C). Freundlich isotherm model and pseudo-second-order kinetics showed better fit for both RB and RR removal from synthetic solution. X-ray diffractogram confirmed the amorphous nature of PPy/Ze nanocomposite and that it was not altered even after dye adsorption. Adsorption–desorption studies showed that the composite has satisfactory adsorption potential for four cycles. The results show that the PPy/Ze nanocomposite could be used for the removal of dyes from wastewaters.

A new molecularly imprinted polymer for selective extraction and pre-concentration of guaifenesin in different samples: Adsorption studies and kinetic modeling.

This paper describes the synthesis of a molecularly imprinted polymer by chemical oxidation of pyrrole as the functional monomer, and at the presence of guaifenesin as the template. The prepared polymer was used as adsorbent in molecularly imprinted solid-phase extraction followed by spectrophotometric determination. Different parameters in the solid-phase extraction including sample pH, adsorbent weight, washing solution, and elution solvent were studied to determine optimum conditions for isolation and enrichment of guaifenesin. The results showed guaifenesin was quantitatively adsorbed on the molecularly imprinted polymer at pH 6.0 and completely eluted with an ethanol-water solution (50% v/v). An enrichment factor of four with satisfactory recoveries (87.0-95.0%) was obtained. The solid-phase extraction columns could be used for up to six consecutive elution-loading cycles without significant decreases in the analyte recoveries. The method had a dynamic range of 3.0×10-6 -1.5×10-4 mol/L with a limit of detection and limit of quantification of 1.4×10-6 and 4.5×10-6 mol/L, respectively. The proposed procedure was used for the extraction and determination of guaifenesin in different pharmaceutical formulations, with satisfying results being achieved.

Preparation and physical properties of polypyrrole/zeolite composites

Abstract Polypyrrole (PPy′)/zeolite composites were synthesized via chemical oxidation of pyrrole in the presence of zeolite. FeCl3 was used as an oxidant with the FeCl3-to-pyrrole molar ratio (MR) equal to 1. The zeolite contents were 0%, 5%, 10%, 15% and 20% of the total weight of PPy′. For comparison, pure PPy″ with FeCl3–pyrrole MR equal to 2 was also synthesized using the same method. The structural and physical properties of the samples were studied using X-rays diffraction (XRD), Fourier transform infrared spectroscopy, field emission electron scanning microscopy, thermogravimetric analysis, van Der Pauw technique and UV–VIS-NIR spectroscopy. The XRD of PPy′/zeolite (5%) revealed a presence of crystalline nature of zeolite in a spectrum of host amorphous PPy′. The XRD peaks increased, became stronger and shifted slightly to higher 2θ in PPy′/zeolite (10–20%) composites. Compared with PPy′, the composites were denser, more compact and had better thermal stability. The composites conductivity increased while their bandgap tended to reduce with increasing of zeolite. PPy′/zeolite (20%) composite had the highest conductivity value of 3.6 S cm−1 with an optical bandgap of 2.21 eV. The results showed that zeolite has been incorporated into PPy′ matrix and improved its physical properties.

Strategies towards the control of one‐dimensional polypyrrole nanomorphology and conductivity

AbstractConducting polypyrrole nanotubes rank among the most conducting polymer materials and find applications in organic electronics and energy conversion devices. They are produced by the chemical oxidation of pyrrole in globular form, which converts to nanotubes or nanofibres in the presence of suitable templates and is often accompanied by a pronounced conductivity increase. This is illustrated by the anionic dye, methyl orange, where the template formation is based on azo–hydrazone tautomerism associated with hydrogen atom transfer caused by the acidity change. In other words, the soluble salt of the dye converts to an insoluble acid, and its one‐dimensional aggregates serve as a locus for the adsorption of pyrrole oligomers. This is followed by the growth of polypyrrole chains constituting the nanotube wall. Safranin, a cationic dye, produces a template by a completely different mechanism, the oxidative generation of insoluble safranin oligomers that perform with similar results. Other mechanisms of template formation are also proposed and discussed but mainly organic dyes have a significant potential to support the one‐dimensional growth of polypyrrole. The role of surfactants that affect the morphology of templates, and subsequently also of polypyrrole, is demonstrated. © 2018 Society of Chemical Industry

8-Hydroxyquinoline aluminum-polypyrrole and 8-hydroxyquinoline aluminum-polyaniline composites: A comparative study on the preparation and property

Polypyrrole (PPy) and polyaniline (PANI)-organometallic complexes were obtained by chemical oxidation of pyrrole and aniline with 8-hydroxyquinoline aluminum (Alq3) using ammonium persulfate as an oxidant. The mechanism of Alq3-PPy and Alq3-PANI composites based on π–π interaction and H-bonding interaction was proposed and proved by the changes in Fourier transform infrared spectroscopy (FTIR) diffraction peaks. The electric conductivity property of conducting composites was measured by means of the four-probe method. FTIR and X-ray diffraction (XRD) results showed that composites with different chemical structures, presented different crystallinity, which resulted in a different electric conductivities. The morphology of composites was observed by scanning electron microscopy (SEM). X-ray photoelectron spectrometer (XPS) and energy dispersive X-ray spectroscopy (EDS) were used for elemental analysis of composites. The optimal reaction condition of the Alq3-PPy and Alq3-PANI composites by in an situ polymerization method was established. It was the first time that the effect of Alq3-PPy and Alq3-PANI composites polymerization conditions on the morphology, structure and properties are comparative studied.

Selective Extraction of Cholesterol from Dairy Samples Using a Polypyrrole Molecularly Imprinted Polymer and Determination by Gas Chromatography

A novel molecularly imprinted polymer (MIP) was prepared by chemical oxidation of pyrrole through applying FeCl3 and was used as a sorbent for selective batch extraction of cholesterol (CHO) in dairy samples. Gas chromatography coupled with flame ionization detector was performed to analyze the samples without any saponification and derivatization treatments. MIP particles were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy techniques. The selectivity of MIP for CHO under competitive adsorption with structurally steroid analogous compounds was investigated and developed polymer showed selectivity toward CHO. The various parameters, such as desorption solvent, the amount of sorbent, pH, and ionic strength, that affect the extraction efficiency of the imprinted polymer were evaluated to optimize the method. Under the optimized conditions, the developed method showed a good linearity in range of 3.75–7000 ng/mL through a correlation coefficient of 0.9952 and 10–120 μg/mL through a correlation coefficient of 0.9921, while good CHO recoveries of 87.3–92.4 % and the limit of detection and the limit of quantification were, respectively, obtained 1.25 and 4.2 ng/mL. The polypyrrole-MIP showed a high extraction efficiency toward CHO compared to the non-imprinted polymer and was successfully used for the determination of CHO in dairy products.

Selective extraction of progesterone hormones from environmental and biological samples using a polypyrrole molecularly imprinted polymer and determination by gas chromatography

A Molecularly Imprinted Polymer (MIP) was chemically prepared for the selective batch extraction of progesterone (PGN) hormones by chemical oxidation of pyrrole using FeCl3.

Electrochemical investigations of polypyrrole aluminum flake coupling

Polypyrrole (PPy) Al flake composite (PAFC) was synthesized by chemical oxidation of pyrrole in the presence of Al flake and was used to formulate a corrosion inhibiting primer. The anticorrosion performance of the PAFC coating for AA 2024-T3 was evaluated by accelerated salt spray, scanning vibrating electrode technique (SVET), galvanic coupling measurement and electrochemical impedance spectroscopy (EIS). The PAFC primer showed an enhanced anticorrosion ability for AA 2024-T3 compared to the Al flake primer and provided cathodic protection for AA 2024-T3 as evidenced by galvanic coupling measurement. A possible corrosion protection mechanism provided by the PAFC and the role of PPy in the formulation were discussed.

Polypyrrole/poly(N‐isopropylacrylamide‐co‐acrylic acid) thermosensitive and electrically conductive composite microgels

AbstractThe electrically conductive polypyrrole/dodecylbenzene sulfonic acid/poly(N‐isopropylacrylamide‐co‐acrylic acid) (PPy/DBSA/poly(NIPAAm‐co‐AA)) composite microgels were synthesized by a chemical oxidation of pyrrole in the presence of DBSA as the primary dopant, and poly(NIPAAm‐co‐AA) microgels as the polymeric codopant and template, in which APS was used as the oxidant. It was proposed to prepare “intelligent” polymer microgel particles containing both thermosensitive and electrically conducting properties. The polymerization of pyrrole took place directly inside the microgel networks, leading to formation of composite microgels and the morphology was observed by transmission electron microscope. PPy particles interacted strongly with microgels, as the acid groups of microgels acted as the polymeric codopant. The composite microgels thus formed showed electrically conducting behavior dependent on humidity and temperature. At temperatures lower than lower critical solution temperature, the conductivity decreased with increasing the humidity and a small hysteresis phenomenon was observed. The hysteresis became indistinct when temperature was near volume phase transition temperature. However, after the treatment of high temperature and high humidity, the conductivity increased surprisingly due to the structure reorganization inside the composite microgels. The distinctive functionality of the PPy composite microgels was expected to be utilized in many attractive applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1648–1659, 2006

Electrochemical activity of chemically deposited polypyrrole films

Conducting polypyrrole (PPY) films are deposited on platinum by chemical oxidation of pyrrole from acid solutions of H2O2, K2S2O8, K2Cr2O7, FeCl3 and Fe2(SO4)3. Cyclic voltammograms and charge–potential data are obtained for these PPY films in 0.1 M LiClO4 and 0.1 M Na2SO4 solutions. Chemically deposited PPY films are electrochemically active and yield oxidation–reduction peak potentials that are similar to those of PPY films electrochemically synthesized in solutions with the same anions. The shape of the cyclic current–potential curves and the charge–potential responses of the chemically deposited PPY depend on the bath composition. The bath determines the counter anion introduced into the PPY film. The physical appearance and thickness of a film depends on the deposition time, acidity and composition of the electroless plating baths.

On the ozone degradation of polypyrrole

Polypyrrole, a conducting polymer, has been treated with ozone in a fixed bed reactor. Two different samples of polypyrrole (PPy) have been studied. PPy-Cl prepared by chemical oxidation of pyrrole with FeCl 3 and PPy-Cl-DBSNa prepared using the same oxidant and an anionic surfactant sodium dodecylbenzenesulfonate (DBSNa). It has been shown by weight increase as function of time, by FT-IR spectroscopy of the samples, and by electronic spectroscopy that the sample PPy-Cl is one order of magnitude more stable toward ozone attack in comparison to the sample PPy-Cl-DBSNa containing the surfactant. The reactivity of polypyrrole with ozone is easily detectable by different techniques. The ozonized polypyrrole samples show a significantly worse thermal stability as measured by TGA-DTA in comparison with the pristine samples demonstrating the profound degradation caused by the exposure to O 3. PPy-Cl has been ozonized also in liquid phase in suspension or solution/suspension in different solvents. The electronic spectroscopy showed that the early stages of the ozonation reaction involve the interaction of ozone with the bipolaron and polaron defects of polypyrrole.

Enhanced Electrochemical Properties of Li Secondary Batteries Using Polypyrrole/LiMn2O4 Composite Cathodes

Polypyrrole(PPy)/LiMn2O4 composites were prepared by chemical oxidation of pyrrole onto LiMn2O4 with dodecylbenzene sulfonate as a dopant. The polymerization occurred mainly on the surface of LiMn2O4 to yield the entirely coated LiMn2O4 particles. The capacity of the cell reached the maximum of 124 mAh/g at 4.1 wt% of PPy in the active material. The composite cell showed enhanced charge-discharge properties compared with a pure LiMn2O4 cell. The PPy may enhance the electron exchange ability and stabilize the structure of LiMn2O4.

A novel thermosensitive soluble polypyrrole composite

Electrically conducting PPy/DBSA/poly(NiPAAm-co-AMPS) composites were synthesized by chemical oxidation of pyrrole using ammonium persulfate (APS) as the oxidant in an aqueous solution. Dodecylbenzene sulfonic acid (DBSA) and a copolymer, poly(NiPAAm-co-AMPS), of N-isopropyl acrylamide (NiPAAm) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) were used as a primary dopant and a co-dopant, respectively. We figured out poly(NiPAAm-co-AMPS) was incorporated into the PPy composite as the co-dopant through sulfate anion of AMPS. When more poly(NiPAAm-co-AMPS) was fed into the polymerization solution, more poly(NiPAAm-co-AMPS) existed in the resulting composite. Most of the composites showed good solubility in chloroform with extra DBSA. From the composite solutions, we cast free-standing films with excellent quality whose electrical conductivities were in the range of 10−2 to 5S/cm.We found the PPy composites exhibited moisture-dependent electrical conduction behavior. Electrical conductivity of the PPy composite increased with increase of moisture concentration in air, which resulted from the moisture absorbed by hydrophilic NiPAAm moiety in the composite. Moisture absorption by NiPAAm was confirmed by higher swelling ratio in water of the composites containing more NiPAAm moiety. We also found PPy/DBSA/poly(NiPAAm-co-AMPS) composites showed thermosensitive swelling behavior in water. The swelling ratios of PPy composites gradually decreased with temperature until 35°C, which is known as the lower critical solution temperature (LCST) of poly(NiPAAm). We, therefore, concluded the decrease of swelling ratio with temperature was caused by release of water from the composite by coagulation of the thermally sensitive NiPAAm moiety in the composite. We expect the moisture-dependent electrical conductivity and thermosensitive swelling behvior of the composite synthesized in this study may be useful for diverse attractive applications.

Polymerization of pyrrole and processing of the resulting polypyrrole as blends with plasticised PVC

AbstractPolypyrrole was synthesized by chemical oxidation of pyrrole in water containing various sulphonic acids like toluene sulphonic acid (TSA), sulphosalicylic acid (SSA), and camphor sulphonic acid (CSA), as well as a combination of each sulphonic acid with sodium dodecyl benzene sulphonate (NaDBS) to investigate the effect of doping on conductivity, yield, and processability of the conducting polymer. Free‐standing blend films of polypyrrole and plasticized polyvinyl chloride (PVC) were obtained by casting an homogeneous suspension of the two polymers in tetrahydrofuran. The maximum conductivity of the blend film is ∼ 0.3 S/cm, corresponding to a weight fraction of 0.16 w/w polypyrrole. The blend film is semiconducting in the range 300–10 K. A TG‐DTA scan indicates the blend film to be amorphous with a stepwise decomposition process similar to pristine PVC. The choice of a dual dopant system during synthesis and the plasticised polymer during subsequent processing were keys to obtaining homogeneous high‐quality films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1544–1548, 2001

Charge-discharge properties of composites of polypyrrole and vanadium oxide powder

Composite of polypyrrole and crystalline V2O5 powder was prepared by chemical oxidation of pyrrole with use of V2O5 powder itself as an oxidizing agent. The V2O5 content was changed from 0 to 94 wt% by changing the amount of V2O5 dispersed in the preparation bath. The pellet electrodes could be prepared by pressing the composite powder alone even if amount of polypyrrole in the composite was only 6 wt%. The resulting pellet electrode exhibited good charge-discharge performance as a positive electrode of Li rechargeable battery in an electrolyte solution as well as in a quasi-solid cell fabricated by using a gel electrolyte sheet of poly(methyl methacrylate).

Surface characterizations of conductive poly(methyl methacrylate)/polypyrrole composites

The composites of poly(methyl methacrylate) and polypyrrole (PMMA/PPy) were prepared by a chemical oxidation of pyrrole in a PMMA latex medium resulting in a network like structure of polypyrrole embedded in the insulating polymer matrix. Water was used as the dispersion medium. The content of polypyrrole was determined by elemental analysis as varying from 0.25 wt.% to 10 wt.%. The electrical conductivity of prepared composites depends on the concentration of polypyrrole and reached values of between 1 × 10− 9 S/cm to 0.1 S/cm The surface of powder form of PMMA/PPy composites was characterized by X-ray photoelectron spectroscopy (XPS) and by scanning electron microscopy (SEM). The antistatic properties of compression moulding form of composites were tested.

Thin polypyrrole films prepared by chemical oxidative polymerization

Polypyrrole (PPY) films with a thickness of 3–4 μm were obtained by chemical oxidation of pyrrole (PY) at the interface of chloroform and water with an oxidant (NH4)2S2O8. The films were compact and could be removed with a solid plate. The quality and compositions of these films varied with the molar ratios of the monomer and oxidant of the reaction systems. Overoxidation of polypyrrole was observed and confirmed by the characterizations via infrared spectra and elemental analysis of the films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2169–2172, 1998

Highly conductive polypyrrole films on non-conductive substrates

We report on a method to deposit thin films of conductive polypyrrole powder on non-conductive substrates. This is a new method in contrast to the usual way of preparing polypyrrole films by anodic deposition on metal substrates. Polypyrrole tosylate is synthesized by chemical oxidation of pyrrole with ammoniumpersulfate in aqueous solution. We optimized the conductivity by variation of the reaction conditions. Then we produced smooth films of polypyrrole by testing several methods of film deposition. All of these samples were characterized by conductivity and by X-ray photoelectron spectroscopy (XPS) measurements, and compared to electrochemically produced polypyrrole films.