Electrochemical properties of microwave irradiated synthesis of poly(3,4-ethylenedioxythiophene)/V2O5 nanocomposites as cathode materials for rechargeable lithium batteries

A series of poly(3,4-ethylenedioxythiophene) (PEDOT)/V₂O₅ nanocomposites are prepared via the redox intercalative polymerization reaction of 3,4-ethylenedioxythiophene (EDOT) monomer and crystalline V₂O₅ within 10 min by using rapid 2.45 GHz microwave irradiation with full power (800 W). The unique properties of the resultant nanocomposites are investigated by various characterization techniques using powder XRD, TGA/DTA and four-point probe conductivity analysis supports the intercalation of polymer nanosheet between V₂O₅ layers leading to enhanced bi-dimensionality. X-ray photoelectron spectroscopy analysis clearly shows the presence of mixed valent V⁴⁺/V⁵⁺ in the V₂O₅ framework after the redox intercalative polymerization which also confirms charge transfer from the polymer to the V₂O₅ framework. The application potential of these composites as cathode materials in rechargeable lithium batteries is also demonstrated by the electrochemical intercalation of lithium into the PEDOT/V₂O₅ nanocomposites, where an enhancement in the discharge capacity (370 mAh/g) is observed compared to that of crystalline V₂O₅.     

Towards TiO2-conducting polymer hybrid materials for lithium ion batteries

Nanocomposites of TiO₂ (anatase) with polypyrrole (Ppy) or poly(3,4-ethylenedioxythiophene) (PEDOT) were prepared via electrochemical routes. The deposition process of the conducting polymer films was performed in the presence of perchlorate, p-toluenesulphonate (TOS) or bis(trifluoromethylsulphonyl)imide (TFSI) anions in propylene carbonate (PC). The obtained electrode materials were characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). An improvement of lithium ion intercalation/de-intercalation properties of titanium(IV) oxide as a result of its interfacing with the polymers is evidenced. This effect was strongly dependent on the thickness of the polymer layer and closely related to the polymer facility for transporting of lithium ion. Polypyrrole properties, in contrast to the PEDOT case, are very sensitive to selection of the substrate material (Pt or Pt/TiO₂) during electropolymerization. Polypyrrole deposited on a rough surface exhibits an improvement in its ion exchange abilities. The impact of underlying TiO₂ layers on Ppy properties has an indirect (synergic) influence on the effectiveness of lithium ion intercalation into the oxide too. The properties of the composites were discussed also in view of the comparative electrochemical quartz crystal microbalance (EQCM) study focussing on ion transport properties of Ppy and PEDOT.     

Electrochemically and vapour grown electrode coatings of poly(3,4-ethylenedioxythiophene) doped with heteropolyacids

Thin films of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with heteropolyacids have been grown electrochemically and by a vapour transport method onto carbon paper supports, both methods employing 12-molybdophosphoric acid and 10-molybdo-2-vanadophosphoric acid as dopants. Coatings deposited potentiodynamically at 100 mV s⁻¹ from mixed 3,4-ethylenedioxythiophene (EDOT) and 12-molybdophosphoric acid or 10-molybdo-2-vanadophosphoric acid gave electrodes stable beyond 1000 voltammetric cycles in aqueous sulfuric acid; vapour grown electrode coatings degraded during cyclic voltammetry.     

Truly solid state electrochromic devices constructed from polymeric ionic liquids as solid electrolytes and electrodes formulated by vapor phase polymerization of 3,4-ethylenedioxythiophene

Using polymeric ionic liquids, namely poly[1-(2-(2-(2-(methacryloyloxy)ethoxy)ethoxy)ethyl)-3-methylimidazolium]bis(trifluoromethylsulfonyl)imide or tetracyanoborate, and poly(3,4-ethylenedioxythiophene) (PEDOT) as an ion conductor and electrodes, respectively, the all-polymer-based thin-film symmetrical electrochromic devices (ECDs) have been constructed and tested. The proposed architecture serves as a prove of concept that polymeric ionic liquids (PILs) can be themselves used as solid electrolytes thus avoiding any electrolyte leakage since the ionic liquid species are grafted on the polymer backbone. Three different methods for the synthesis of PEDOT electrode films, including two new approaches consisted in vapor phase polymerization of 3,4-ethylenedioxythiophene (EDOT) in the presence of ionic monomer and poly(ethylene glycol)(di)methacrylates, have been investigated. Two oxidants, Fe[(CF₃SO₂)₂N]₃ and Fe[(CN)₄B]₃, bearing the same anions as PILs were prepared for the first time and utilized in the vapor phase polymerization of EDOT. It was found that the more compact structure and the highest conductivity are achieved for PEDOT electrodes prepared by vapor phase polymerization of EDOT in the presence of ionic monomer and poly(ethylene glycol)(di)methacrylates, followed by radical polymerization of the latters. The simplicity of ECDs assembly, their fast switching times (3–5 s), high coloration efficiency (up to 430 cm²/C), satisfactory optical contrast (up to 28.5%), absence of any liquids and good performance in air and in vacuum were found among the advantages of the proposed technology.     

Electrosynthesis and properties of poly(3,4-ethylenedioxythiophene) films functionalized with titanocene dichloride complex

Synthesis of a titanocene dichloride derivative functionalized with 3,4-etylenedioxythiophene group, Tc1EDOT (Cl₂TiCpC₅H₄(CH₂) (3,4-ethylenedioxythiophene)) has been described. Redox behavior of the monomer in tetrahydrofuran (THF), dichloromethane (DCM) and acetonitrile (AN) at different scan rates has been discussed in terms of different ability of these solvents to coordination with the reduced titanocene (Tc) complex and the solvation of Cl⁻ anions. Electrooxidation of Tc1EDOT to get a conducting polymer film with immobilized titanocene dichloride centers and electrochemical properties of its polymer matrix in background acetonitrile solution have been compared with those of non-substituted PEDOT and PEDOT-methanol derivative (PEDOTMet), to elucidate the effect of substituents both on polymerization and redox potentials of the matrix. STM and AFM images of p(Tc1EDOT) films obtained with potentiodynamic and potentiostatic regimes are compared to illustrate that the films deposited at constant potential are better ordered and more compact than those obtained by cyclic voltammetry. A comparison of the cyclic voltammograms of p(Tc1EDOT) and poly(titanocene-propyl-pyrrole) (p(Tc3Py)) films in 0.1 TBAPF₆ in THF has shown that the electroactivity of the polymer matrix of p(Tc1EDOT) is extended to more negative potentials in comparison to that of p(Tc3Py). This results in the anodic shift of redox potential of Tc centers immobilized in p(Tc1EDOT) film with respect to that of the centers fixed in p(Tc3Py).     

Hole transport in conducting ultrathin films of PEDOT/PSS prepared by layer-by-layer deposition technique

Multilayered ultrathin films of a conductive polymer, poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) were prepared by layer-by-layer deposition technique. These films were characterized by absorption spectroscopy, atomic force microscopy, cyclic voltammetry and potential step chronoamperometry. The PEDOT/PSS films were layered up with a bilayer thickness of 5 nm and the surface roughness of the films was improved after the ultrasonicated pretreatment of a PEDOT/PSS aqueous dispersion prior to the deposition. The ultrathin films thus obtained kept excellent diffusion constant of hole carriers, 5×10⁻¹⁰ cm² s⁻¹, as high as that of spin-cast films of PEDOT/PSS, indicating that the conducting polymer films are fabricated with nanometer-scale precision and act as a junction layer between the electrode and electrochemically active organic materials.     

Electrosynthesis of poly(3,4-ethylenedioxythiophene) microcups in the aqueous solution of LiClO4 and tri(ethylene glycol)

In this paper, we report a novel route for electrochemical growth of poly(3,4-ethylenedioxythiophene) (PEDOT) microcups with diameters in the range of 1-4 μm. In the process, 3,4-ethylenedioxythiophene (EDOT) was dispersed as microdroplets in the aqueous solution of LiClO₄ and tri(ethylene glycol) (TEG) by sonication. Then, the microdroplets were assembled on the indium tin oxide (ITO) glass electrode modified with multilayers poly(diallyldimethylammonium chloride) (PDDA) and poly(4-styrenesulfonic acid) (PSS), and polymerized into microcups. The well-ordered microcups stand on the working electrode surface in a density of about 10⁶ units cm⁻².     

Electrophoretic Display of surface modified TiO<Subscript>2</Subscript> driven by Poly (3,4-ethylenedioxythiophene) Electrode

Summary Electrophoretic display system was fabricated to investigate the effectiveness of transparent polymer electrode using Poly (3,4-ethylenedioxythiophene) (PEDOT). The electrophoretic TiO₂ nanoparticles were coated to modify the surface. As a transparent polymer electrode, 3,4-ethylenedioxythiophene (EDOT) was in-situ polymerized into PEDOT. When the reducing agent (N-dimethylacetamide, DMAc) was added, surface resistivity of PEDOT was dominantly reduced. With the DMAc addition of 40 wt % to the monomer content, surface resistivity was as low as 100 Ω/□, and transmittance was almost 80% in visible ray region.     

Electrical conductivity of poly(3,4-ethylenedioxythiophene):p-toluene sulfonate films hybridized with reduced graphene oxide

Reduced graphene oxide-poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (rGO-PEDOT:PTS) hybrid electrode films were synthesized directly on a substrate by interfacial polymerization between an oxidizing solid layer and liquid droplets of 3,4-ethylenedioxythiophene (EDOT) produced by electrospraying. The EDOT reduced the graphene oxide by donating electrons during its transformation into PEDOT:PTS, and hybrid films consisting of rGO distributed in a matrix of PEDOT:PTS were obtained. These rGO-PEDOT:PTS hybrid films showed excellent electrical conductivities as high as 1,500 S/cm and a sheet resistance of 70 Ω sq^-1. The conductivity values are up to 50% greater than those of films containing conductive PEDOT:PTS alone. These results confirm that highly conductive rGO-PEDOT:PTS hybrid films can potentially be used as organic transparent electrodes.     

PEDOT: Cathode active material with high specific capacity in novel electrolyte system

Poly(3,4-ethylenedioxythiophene) (PEDOT) was chemically synthesized and characterized by FT-IR, XRD, XPS, TGA and organic elemental analysis (EA). The polymer was tested as cathode active material for rechargeable lithium batteries. The cyclic voltammetry (CV) and charge–discharge tests of PEDOT as the cathode active material was investigated in an electrolyte system of LiN(CF₃SO₂)₂/1,2-dimethoxyethane/1,3-dioxopentane (1:2 by weight). The peak discharge capacity of up to 691 mAh/g was obtained during the 1st cycle, and remained above 330 mAh/g after 44 cycles. These results indicate that PEDOT can afford a high specific capacity as a cathode active material. A redox mechanism is tentatively proposed.     

Preparation and characterisation of poly(3,4-ethylenedioxythiophene) and poly(3,4-ethylenedioxythiophene)/poly(neutral red) modified carbon film electrodes, and application as sensors for hydrogen peroxide

Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared for the first time on carbon-film electrodes (CFE) in aqueous solution using electropolymerisation by potential cycling, potentiostatically and galavanostatically. Characterisation of the modified electrodes was done by cyclic voltammetry and electrochemical impedance spectroscopy and the stability of the polymer films was probed. The coated electrodes were tested for application as hydrogen peroxide sensors, by oxidation and reduction. A novel polymer film was also formed by modification of CFE by co-electropolymerisation of EDOT and the phenazine dye neutral red (NR) – (PEDOT/PNR) with a view to enhancing the properties for sensor applications. It was found that hydrogen peroxide reduction at the PEDOT/PNR coated electrodes could be carried out at a less negative potential, the sensor performance comparing very favourably with that of other polymer-modified electrodes reported in the literature.     

Electrochemical and spectroelectrochemical study on bilayer films composed of C60 and poly(3,4-ethylenedioxythiophene) PEDOT

Bilayers of drop casted C₆₀ fullerene films and electrochemically synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) films have been studied. The PEDOT film was polymerised by cyclic voltammetry on top of the drop casted C₆₀ fullerene film. The bilayer films were produced and characterized in three different electrolytes; tetrabutylammoniumhexafluorophosphate (TBAPF₆) and lithium hexafluorophosphate (LiPF₆) in acetonitrile (ACN) and in the ionic liquid 1-butyl-3-methyl-imidazolium tetrafluoroborate (BMIMBF₄). The bilayers were studied by cyclic voltammetry and in situ Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy. Both p- and n-doping of the bilayer films were studied and compared with PEDOT films prepared in organic media.     

Solid-state electrochromic devices using pTMC/PEO blends as polymer electrolytes

Flexible, transparent and self-supporting electrolyte films based on poly(trimethylene carbonate)/poly(ethylene oxide) (p(TMC)/PEO) interpenetrating networks doped with LiClO₄ were prepared by the solvent casting technique. These novel solid polymer electrolyte (SPE) systems were characterized by measurements of conductivity, cyclic voltammetry, differential scanning calorimetry and thermogravimetry.The incorporation of solid electrolytes as components of electrochromic devices can offer certain operational advantages in real-world applications. In this study, all-solid-state electrochromic cells were characterized, using Prussian blue (PB) and poly-(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT) as complementary electrochromic compounds on poly(ethyleneterphthalate) (PET) coated with indium tin oxide (ITO) as flexible electrodes. Assembled devices with PET/ITO/PB/SPE/PEDOT/ITO/PET “sandwich-like” structure were assembled and successfully cycled between light and dark blue, corresponding to the additive optical transitions for PB and PEDOT electrochromic layers. The cells required long cycle times (>600 s) to reach full color switch and have modest stability towards prolonged cycling tests. The use of short duration cycling permitted the observation of changes in the coloration-bleaching performance in cells with different electrolyte compositions.     

High-quality freestanding flexible poly(5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1H-indole) film: Electrosyntheses,characterization, and optical properties

The electron-donating substituted indole is generally difficult to be polymerized into high-quality film. The electrochemical polymerization of the electron-donating 3,4-ethylenedioxythiophene (EDOT)-monosubstituted indole may be a challenge. Herein, we designed and synthesized a novel fluorescent comonomer based on the combination of indole and EDOT groups, namely, 5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1H-indole (EDTI), and subsequently electrodeposited into flawless freestanding flexible poly(5-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1H-indole) (PEDTI) film with a resistance of 60 MΩ/cm in CH₂Cl₂ containing 0.1 M Bu₄NBF₄. Electrochemical results showed that the oxidation onset potential of EDTI was at 0.8 V vs Ag/AgCl, which was lower than those of indole (0.96 V vs Ag/AgCl) and EDOT (1.35 V vs Ag/AgCl). FTIR spectra indicated that the polymerization of EDTI occurred at the 5-position on thiophene ring and 2,3-positions on indole ring, forming the crosslinking polymer film. The colors of as-prepared PEDTI could switch reversibly from purple to brown under applied potentials of 1.3 and −1.3 V, which were distinctly different from those of polyindole, poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(EDOT-bis-substituted indole) (PETI). Fluorescence spectral studies revealed that the comonomer and corresponding polymer were good blue-green light emitters. These results implied that PEDTI had potential applications for photoelectric devices such as electrochromic devices, light-emitting diodes, and fluorescence sensors. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47016.     

Surface polymerization of (3,4-ethylenedioxythiophene) probed by in situ scanning tunneling microscopy on Au(111) in ionic liquids

The electropolymerization of 3,4-ethylenedioxythiophene (EDOT) to poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated in the air and water-stable ionic liquids 1-hexyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate [HMIm]FAP and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide [EMIm]TFSA. In situ scanning tunnelling microscopy (STM) results show that the electropolymerization of EDOT in the ionic liquid can be probed on the nanoscale. In contrast to present understanding, it was observed that the EDOT can be oxidised in ionic liquids well below its oxidation potential and the under potential growth of polymer was visualized by in situ STM. These results serve as the first study to confirm the under potential growth of conducting polymers in ionic liquids. Furthermore, ex situ microscopy measurements were performed. Quite a high current of 670 nA was observed on the nanoscale by conductive scanning force microscopy (CSFM).     

Preparation of thermally curable conductive films PEDOT:P(SS-NMA) and their performances on weather stability and water resistance

In this research, sodium 4-styrenesulfonate (SSNa) and N-(methylol acrylamide) (NMA) were copolymerized to form the thermally curable copolymer P(SS-NMA). Moisture absorptivity and swelling index were used to evaluate the weather stability of P(SS-NMA). The P(SS-NMA) copolymers with high molar content of NMA exhibited better weather stability. Then, P(SS-NMA) was used as the polymeric template to carry out the oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) and yielded the thermally curable conductive dispersion, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate-N-(methylol acrylamide)) (PEDOT:P(SS-NMA)). The optoelectronic property and surface morphology for the PEDOT:P(SS-NMA) conductive thin films were investigated. In addition, the performance of the PEDOT:P(SS-NMA) conductive film was characterized in the two parts: weather stability and water resistance. The introduction of crosslinking structures into the conductive film improved the mechanical property and weather stability so as to resolve the drawbacks of the commercial products PEDOT:PSS.     

Synthesis and electro-optical properties of a new copolymer based on EDOT and carbazole

A new copolymer of 3,4-ethylenedioxythiophene (EDOT) and 5-(2-ethylhexyl)-1,3-bis(9-methyl-9H-carbazol-3-yl)-5H-thieno[3,4-c]pyrrole-4,6-dione (CzPDICz) was electrochemically synthesized using different monomer feed ratios. The resulting copolymer films were investigated in terms of their electrochemical and electro-optical behaviors. Properties of the obtained copolymer films through different monomer feed ratios were compared to each other and to individual poly(ethylenedioxythiophene; PEDOT) and homopolymer of CzPDICz in order to observe the differences in the properties with respect to PEDOT and P(CzPDICz). Copolymers exhibited well adherence on the electrode surface with having non-diffusional redox process. The monomer feed ratios were prepared as 9:1; 4:1, and 1:1 (EDOT:CzPDICz) and changes in the electrochemical and spectroelectrochemical behavior were noted with increasing CzPDICz ratio in the monomer mixture. Although no appreciable change in the optical band gap values of the copolymers was noted as compared to PEDOT, the neutral blue copolymers exhibited grayish color in their semi-oxidized states and transparent green in their fully oxidized states.     

Effect of polymerization potential on the actuation of free standing poly-3,4-ethylenedioxythiophene films in a propylene carbonate electrolyte

The linear actuation of poly-3,4-ethylenedioxythiophene (PEDOT) films polymerized at different potentials (0.8-1.3 V) at −27 °C in propylene carbonate (PC) solutions of TBACF₃SO₃ (tetrabutylammonium trifluoromethanesulfonate) was examined under isotonic (constant force) and isometric (constant length) conditions. The actuation properties were evaluated by electrochemomechanical deformation measurements (ECDM) during cyclic voltammetry, square wave potential steps and long term cycling. The ECDM response revealed mixed ion actuation behaviour for PEDOT films polymerized at the potential extremes of 0.8 and 1.3 V. At intermediate polymerization potentials from 0.9 to 1.2 V, cation-driven actuation was observed involving immobilized triflate anions (CF₃SO₃⁻). Long term experiments (50 cycles) showed that films prepared at polymerization potentials of 0.8 V exhibited mainly anion-driven actuation, during potential steps to and from 1.0 V; conversely PEDOT prepared at a polymerization potential of 1.1 V showed exclusively cation-driven actuation. PEDOT films prepared at a polymerization potential of 1.1 V showed the maximum cation-driven actuation during cyclic voltammetry experiments including long term cycling. SEM images showed an open porous structure in all of the PEDOT films.     

Self-supported semi-interpenetrating polymer networks for new design of electrochromic devices

This paper reports the preparation of conducting films combining linear poly(3,4-ethylenedioxythiophene) (PEDOT) and cross-linked polyethylene oxide (PEO) into semi-interpenetrating networks. Due to the synthetic pathway, PEDOT is distributed within the PEO matrix and specifically along the two outer faces of the film. Such a distribution of the conducting polymer inside the matrix leads to the design of a self-supported and symmetrical PEDOT-Polymer electrolyte-PEDOT electrochromic device which can substitute the usual multilayer configuration. Optical contrast ΔT_630 nm (%) up to 33% is reached without contrast loss after 1500 switches. The switching time is 30 s for bleaching with a good memory effect (less than 1% decrease of transmittance after 1 h) of the device.     

Light induced electropolymerization of poly(3,4-ethylenedioxythiophene) on niobium oxide

The photoelectrochemical polymerization of poly(3,4-ethylenedioxythiophene), PEDOT, was successfully realized on anodic film grown to 50 V on magnetron sputtered niobium. Photocurrent Spectroscopy was employed to study the optical properties of Nb/Nb₂O₅/PEDOT/electrolyte interface in a large range of potential, and to get an estimate of the band gap and flat band potential of both the oxide and the polymer. Scanning Electron Microscopy was used to study the morphology of PEDOT. Both the optical and morphological features of the photoelectrochemically grown polymer were compared with those showed by PEDOT electropolymerized on gold conducting substrate.