Chemical and electrochemical polymerisation of pyrrole on polyester textiles in presence of phosphotungstic acid

Polypyrrole (PPy) was chemically synthesised on polyester (PES) textiles to produce conducting textiles. Two different types of counter ion were employed: anthraquinone sulfonic acid (AQSA) and phosphotungstate (). Textiles covered with PPy were characterised by means of FTIR-ATR, SEM, EDX, cyclic voltammetry (CV), surface resistivity measurements and electrochemical impedance spectroscopy (EIS). Additionally, friction and washing assays were done to test the resistance of the layer of conducting polymer (PPy/). Electropolymerisation of PPy/ in acetonitrile medium onto chemically synthesised PES-PPy/ showed the improvement of the coating properties.     

Electrochemical synthesis of polypyrrole/polyimide conducting composite using a polyamic acid precursor

Conducting polymer/poly(amic acid) composites were synthesized by casting poly(amic acid) (PAAc)film onto the surface of stainless steel followed by electrochemical deposition of polypyrrole. Polypyrrole/polyimide (PPy/PI) composites were also formed by preimidizing the polyamic acid film prior to electrodeposition of PPy. The electrical resistance of the bottom side of PPy/PAAc composite (2.3 Ω cm) was lower than that of the PPy/PI composite (6.4 Ω cm), the thickness of the matrix was the same. A PI matrix was used for electropolymerization of pyrrole. The electrodeposition was investigated by using different current densities. IR spectroscopy revealed interactions between the PAAc and PPy in the composite.     

Stability of conducting polyester/polypyrrole fabrics in different pH solutions. Chemical and electrochemical characterization

The stability of conducting fabrics of polyester (PES) covered with polypyrrole/anthraquinone sulfonic acid (AQSA) has been tested in different pH solutions (1, 7, 13) and after washing tests. It is important to determine the stability of the counter-ion in the polymer matrix, since its loss causes the decrease of the conducting properties of the fabrics. X-ray photoelectron spectroscopy (XPS) studies were done to quantify the amount of counter-ion in the polymer and to obtain the doping level (N^δ+/N). Surface resistivity changes after the different tests were measured by electrochemical impedance spectroscopy (EIS). An increase in the solution pH caused a decrease of the doping level (N^δ+/N), the release of part of the counter-ions and an increase in the surface resistivity. Cyclic voltammetry (CV) measurements showed a gradual loss of electroactivity as pH increased. The influence of the scan rate on the characterization of conducting fabrics has been also demonstrated by CV. Lower scan rates produce a more characteristic response than higher ones. Scanning electrochemical microscopy (SECM) measurements showed a loss of electroactivity when the sample was tested in the pH 13 solution, although the material continued being electroactive.     

Biodegradability of conducting chitosan-g-polycaprolactone/polypyrrole conduits

Conducting chitosan-g-polycaprolactone(CPC)/polypyrrole(PPy) conduits were fabricated for potential applications in nerve repair. Their mechanical and conducting properties as well as in vitro and in vivo degradation behaviors were mainly examined. It was found that some CPC/PPy conduits showed significantly stronger tensile and lateral compressive strength in the wet state, and notably higher conductivity in the overall tested PPy-load range, in comparison with chitosan/PPy conduits. After being consecutively exposed to PBS systems for various periods up to 10 weeks, the CPC/PPy conduits exhibited relatively slow degradation compared to chitosan/PPy conduits, and their degradation behaviors were measurably mediated by the composition of CPCs. The pH values of media corresponding to some selected CPC/PPy conduits did not significantly deviate from the initial pH value due to the buffering effect of chitosan component. After being implanted into rabbits for various periods, it was observed that the explanted chitosan/PPy conduits could only sustain a very low compressive load after 6-week degradation, and most of them were partially or fully collapsed after 8-week or longer degradation and showed very low conductivity. In contrast to these observations, some explanted CPC/PPy conduits were able to maintain enough strong mechanical strength in the wet state for the required period, and still showed acceptable conducting properties after 10-week in vivo degradation. Results suggested that some CPC/PPy conduits having proper compositional proportions could serve as desirable candidates to bridge nerve gaps in vivo.     

AFM study of conducting polymer polypyrrole nanoparticles formed by redox enzyme - glucose oxidase - initiated polymerisation

Redox enzyme – glucose oxidase E.C. 1.1.3.4 from Penecillum vitale (GOx) – initiated polypyrrole (Ppy) synthesis was applied for the formation of polypyrrole based nanoparticles. The increase in optical absorbance at λ = 460 nm was exploited for the monitoring of polypyrrole polymerisation process. The shape and size of the formed Ppy nanoparticles was also monitored by means of contact mode AFM. The highest increase in the diameter of the formed Ppy nanoparticles was detected during 15-day period. AFM imaging was performed in contact mode to investigate the shape and flexibility of particles deposited on the SiO₂ and Pt surfaces. Contact mode AFM investigations allowed us to conclude that after drying at 50 °C the formed Ppy particles are more flexibly deposited on the Pt electrode if compared to those deposited on the SiO₂ substrate. The application of well-shaped Ppy nanoparticles in biomedicine, chromatography and bioanalysis may be predicted.     

Composites of polypyrrole with conducting and ferromagnetic behaviors

Composites of polypyrrole (PPy) with electrical and ferromagnetic behaviors were synthesized by a chemical method in the presence of p‐dodecylbenzene sulfonic acid sodium salt (NaDS) as a surfactant and dopant. The magnetic properties of the resulting composites showed ferromagnetic behavior, such as high saturated magnetization (M_s = 3.06–43.7 emu/g), and coercive force (H_c = 9–57 Oe). The saturated magnetization linearly increased with increases in the Fe content. No influence of the counterion on this relationship was observed. The conductivity of the composites at room temperature depended on the counterion and doping degree. The highest conductivity of 10⁰ S/cm was achieved under the optimal synthetic conditions. A structural characterization by elemental analysis, Fourier transform infrared, and X‐ray diffraction proved that nanometer‐sized (16–20‐nm) iron oxide (Fe₃O₄) in the composites was responsible for the ferromagnetic behavior of the composites, whereas the high conductivity of the composites contributed to the difficult deprotonation of the doping PPy with DS⁻ counterion in a basic reaction medium. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2734–2739, 2000     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

Versatile functionalization of polyester hydrogels with electroactive aniline oligomers

Functionalizing aliphatic polyester hydrogels with an aniline oligomer is a means of achieving electrically conductive and degradable hydrogels. To lower the aniline oligomer content while maintaining a high conductivity and to overcome the acidic degradation product from polylactide reported in our previous work, a series of electroactive and degradable hydrogels based on polycaprolactone (PCL) hydrogels and carboxyl‐capped aniline pentamer (CCAP) were synthesized by a simple coupling reaction at room temperature. The reaction was carried out between the hydroxyl groups of hydroxyethylmethacrylate in a photopolymerized glycidyl methacrylate (GMA)‐functionalized PCL‐poly(ethylene glycol)‐PCL degradable network and carboxyl group of CCAP, using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide as water‐condensing agent and 4‐dimethylaminopyridine as catalyst. The electroactivity of the hydrogels was verified by cyclic voltammetry, which showed three pairs of redox peaks. The electrical conductivities and swelling ratios of these hydrogels were controlled by the CCAP content, the poly(ethylene glycol) molecular weight in the macromer, and the crosslinking density of the hydrogels. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Controllable synthesis of conducting polypyrrole nanostructures

Wire-, ribbon-, and sphere-like nanostructures of polypyrrole have been synthesized by solution chemistry methods in the presence of various surfactants (anionic, cationic, or nonionic surfactant) with various oxidizing agents [ammonium persulfate (APS) or ferric chloride (FeCl3), respectively]. The surfactants and oxidizing agents used in this study have played a key role in tailoring the nanostructures of polypyrrole during the polymerization. It is inferred that the lamellar structures of a mesophase are formed by self-assembly between the cations of a long chain cationic surfactant [cetyltrimethylammonium bromide (CTAB) or dodeyltrimethylammonium bromide (DTAB)] and anions of oxidizing agent APS. These layered mesostructures are presumed to act as templates for the formation of wire- and ribbon-like polypyrrole nanostructures. In contrast, if a short chain cationic surfactant octyltrimethylammonium bromide (OTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonylphenyl ether (Opi-10) is used, sphere-like polypyrrole nanostructures are obtained, whichever of the oxidizing agents mentioned above is used. In this case, micelles resulting from self-assembly among surfactant molecules are envisaged to serve as the templates while the polymerization happens. It is also noted that, if anionic surfactant sodium dodeyl surfate (SDS) is used, no characteristic nanostructures of polypyrrole were observed. This may be attributed to the doping effect of anionic surfactants into the resulting polypyrrole chains, and as a result, micelles self-assembled among surfactant molecules are broken down during the polymerization. The effects of monomer concentration, surfactant concentration, and surfactant chain length on the morphologies of the resulting polypyrrole have been investigated in detail. The molecular structures, composition, and electrical properties of the nanostructured polypyrrole have also been investigated in this study.     

导电聚吡咯膜电极的现场电化学-ESR研究

本文报导聚吡咯(PP)膜电极在水溶液中的电化学─ESR行为, 定性地探讨了电位,电量对PP膜中极化学形成与转化过程的影响, 并在PP膜/溶液界面存在电化学反应的情形下, 考察了PP膜中可能的电荷传输机理。     

Electrochemical polymerisation of 2-aminofluorene in ethylalcohol/water medium

Electrochemical polymerisation of 2-aminofluorene, 2AF, was investigated in ethylalcohol/water mixture (3:2, v:v) in the presence of HClO₄ as the supporting electrolyte via constant potential electrolysis, CPE. Prior to CPE, electrochemical behaviour of the monomer was investigated in the same solvent-electrolyte couple utilising cyclic voltammetry, CV. Electrochemical polymerisation of the monomer yielded insoluble, dark bluish-green, conducting polymer deposit on the electrode surface. Characterisation of the polymer film has been carried out using FT-IR spectroscopic technique and thermal behaviour was studied using differential scanning calorimetry, DSC. Spectroelectrochemical, SPEL, behaviour of the polymer on ITO working electrode was studied by recording the electronic absorption spectra, in situ, in monomer-free solution at different potentials and it is found that the film can be reversibly cycled between −0.1 and 1.1 V vs SCE. Paramagnetic behaviour of the polymer was monitored using in situ ESR spectroscopy. The temperature dependence of conductivity supported the Mott's variable range hopping, VRH, mechanism for poly(aminofluorene), PAF.     

Electrochemical behavior of polypyrrole/ kodak aq composite polymeric films

The anodic polymerization of pyrrole (P) onto glassy carbon in an aqueous solution of the Kodak-AQ poly(ester sulfonic acid) polyelectrolyte gives a PP/AQ composite film. While incorporated as charge compensators during the anodic growth of PP, the entangled AQ⁻ chains cannot easily diffuse out upon reduction. The composite layer, resulting from such unique use of AQ ionomers (as electrolyte and dopant) possesses the features of both its conducting polymer and cation exchanger components. These include effective loading of hydrophobic cations, potential switch effect or permselective response. For example, the uptake of Ru(bpy)²⁺₃ by the AQ anion, residing in the conducting polymer, is facilitated by an electrochemical event (reduction of the film to PP⁰/AQ⁻). Similarly, the redox switchable PP component offers electrochemical control of the release of loaded cations. These and other attractive properties of PP/AQ composite layers are explored by cyclic voltammetry, chronocoulometry, potentiometry and flow injection amperometry.     

Functional layers for chemical sensors based on conducting polypyrrole

Functional thin layers based on polypyrrole were used in electrochemical sensors as mixed conducting interfaces between ion‐selective membranes and the wiring. In particular, new types of ion‐selective electrodes for potentiometric measurement of pH value and concentration of sulfate ions in solutions were developed. The resulting electrodes do not need any inner liquid junction. First determinations of the sensor parameters sensitivity, selectivity and long term stability indicate a good performance of the prepared sensors. The results imply that interfaces, containing polypyrrole, could be an interesting basis for the construction of a new type of all‐solid‐state ion‐selective electrodes.     

Electrochemical modulation of sickle cell haemoglobin polymerisation

Sickle cell haemoglobin (HbS) differs from normal haemoglobin by a single amino acid in its beta chain. This amino acid replacement, from glutamic acid to valine, causes polymerisation of proteins into defined long insoluble fibres with a typical diameter of 21.5 nm. The polymerisation is triggered by the formation of deoxyhaemoglobin (deoxyHb) from oxyhaemoglobin (oxyHb) in low oxygen partial pressures, which results in a conformational change in the secondary structure of the protein. We describe an electrochemical method to modulate the oxygen concentration in an optically transparent thin layer cell to produce deoxyhaemoglobin whilst monitoring the extent of polymerisation using turbidity measurements. The oxygen is depleted in the vicinity of the electrode and triggers the polymerisation. The kinetics of polymerisation were investigated using a model for fibrillogenesis describing a two-step process of nucleation followed by elongation. Rate constants describing the nucleation and growth at monomer concentration of 300 mg cm(-3) (4.65 x 10(-3) M) were determined to be 9.45 (+/-0.08) x 10(-6) s(-1) and 1.22 (+/-0.03) x 10(-3) s(-1) respectively, showing that nucleation was far slower than the growth. A similar difference between the rate constants for the nucleation (2.99 (+/-0.4) x 10(-8) s(-1)) and growth (1.08 (+/-0.2) x 10(-3) s(-1)) was seen at monomer concentration of 50 mg cm(-3) (7.75 x 10(-4) M). These results show that nucleation was monomer concentration dependent; however growth was largely independent of monomer concentration. In this study we present a methodology that may be used as a screening method for substances that effect the fibre nucleation and or growth that could be valuable to the pharmaceutical industry for treating sickle cell disease.     

Electrochemical synthesis of novel polypyrrole microstructures

Polypyrrole microstructures with unusual morphologies have been synthesized by direct electrochemical oxidation of pyrrole in beta-naphthalenesulfonic acid aqueous solution.     

Bifunctionality of chemical sensors based on the conducting polymer polypyrrole

Responses of polypyrrole based ion-selective chloride electrode were investigated in chloride and redox media. Bifunctional character of the potentiometric response of the polypyrrole films doped with chloride ions was observed being sensitive both to chloride ions and to the redox potential of the solution, however the redox response seems to predominate.     

Electrochemical copolymerization of thiophene and aniline

In this study homopolymer, copolymer, and composites of aniline and thiophene were synthesized in nitrogen atmosphere by using TEATFB (Tetraethyl ammonium tetrafluoroborate) and Lithium perchlorate as supporting electrolytes. In order to analyze their structure and characteristics, IR spectrums of the samples were taken and thermogravimetric analysis (TGA) was applied. Also, the samples were photographed under scanning electron microscope (SEM) for microstructure analysis and their electrochemical properties were observed and conductivities were obtained by four probe method. Homopolymerization and copolymerization reactions were carried out in two different solvents viz. acetonitrile and benzonitrile in order to see the solvent effect on polymerization. However, changing the solvent was found to have no significant effect on the resulting properties. It was concluded that changing the supporting electrolyte caused a structural difference in the resulting homopolymer. It also affects the properties considerably. During the bilayer preparation changing the coating turn led to variations in the properties of the samples. When polythiophene (PT) was coated with polyaniline (PA), the resulting system was a composite. However, in coating PA with PT the system was identified to be a copolymer. © 1996 John Wiley & Sons, Inc.     

Electrochemical performance of polypyrrole nanorods/functionalized graphene composites for supercapacitors

Journal of Solid State Electrochemistry - Polypyrrole (PPy) hybrid composites are prepared with nitrogen-functionalized graphene (NFG) via in situ polymerization of pyrrole in the presence of NFG...     

Synthesis of conducting polypyrrole by radiolysis polymerization method

Conducting polypyrrole (PPy) has been synthesized by the in situ gamma radiation‐induced chemical oxidative polymerization method. This method takes advantages of the specialties of radiation‐induction, and a highly uniform polymer morphology was obtained. The resultant nanosize polypyrrole particles were characterized by Elemental Analysis, Fourier transform infrared (FT‐IR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and X‐ray Diffraction (XRD). Measurements of polymer particle sizes were obtained at <500 nm. A standard four‐point probe revealed that the chemical synthesis of PPy has a good electrical property. Also thermal stability, checked by Thermal Gravimetric Analysis in air, was ensured by this novel synthesis. Copyright © 2007 John Wiley & Sons, Ltd.     

Electrochemistry of conducting polypyrrole films containing cobalt porphyrin

The electrochemical polymerisation of pyrrole-substituted cobalt tetraphenylporphine complex on a vitreous carbon electrode has been performed in acetonitrile+tetrabutylammonium tetrafluoroborate solution. The redox properties of the film have been examined by cyclic voltammetry and compared to those of cobalt-porphyrin monomer in solution. Voltammograms of these films exhibit a reversible process for the Co(II)/Co(I) reaction at a formal potential of −0.87 V/SCE. The cobalt-porphyrin content of the films has been estimated by cyclic voltammetry, and the conductivity of the polymers has been assessed by studying well-known electrochemical processes in solution at these modified electrodes. Thus, it appears that thick polyporphyrin films act as insulators in low potential range E < −1 V/SCE. Copolymerisation of the pyrrole-substituted cobalt porphyrin with pyrrole and 3-(pyrrol-1-ylmethyl)pyridine has been achieved. No improvement of the electrochemical properties has been noted for the copolymers obtained. We have also proved that interchain complexation reaction of the cobalt(III) sites occurs by the pyridine moieties of the copolymer films.