Electrochemical Polymerization Of 3,4-ethylenedioxythiophene Research Articles

Templating Effect of Water-Soluble Anionic Phthalocyaninate on the Electropolymerization of 3,4-Ethylenedioxythiophene.

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) was performed in the presence of a water-soluble anionic copper and zinc octa(3',5'-dicarboxyphenoxy)phthalocyaninate containing 16 ionogenic carboxylate groups. The influences of the central metal atom in the phthalocyaninate and EDOT-to-carboxylate group ratio (1:2, 1:4, and 1:6) on the course of electropolymerization were studied using electrochemical methods. It has been shown that the polymerization of EDOT in the presence of phthalocyaninates proceeds at a higher rate compared to that in the presence of a low-molecular-weight electrolyte (sodium acetate). Studies of the electronic and chemical structure using UV-Vis-NIR and Raman spectroscopies showed that the use of copper phthalocyaninate leads to a higher content of the latter in PEDOT composite films. The 1:2 EDOT-to-carboxylate group ratio was found to be optimal for a higher content of phthalocyaninate in the composite film.

Construction of Interface Dipoles by Surface Doping and Their Role in the Open Circuit Voltage in Polymer Solar Cells

A kind of dipolar interface is realized by surface doping of poly-(3,4-ethylenedioxythiophene) (PEDOT) with tetrafluoro-tetracyano-quinodimethane (F4TCNQ). PEDOT is in situ synthesized by electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on an indium tin oxide (ITO) electrode, and then F4TCNQ is spin-coated atop the PEDOT layer. Because the LUMO of F4TCNQ is lower than the HOMO of PEDOT, the spontaneous electron transfer from PEDOT to F4TCNQ results in a bilayered structure of PEDOT cations and F4TCNQ anions. Thus, a permanent interfacial dipole is formed in the surface-doping system. The surface doping not only enhances the conductivity of PEDOT, but also increases the surface work function of the electrode. The dipolar film is applied as the anode interface in polymer solar cells (PSCs), and the results show that such an interface dipole plays a very important role in the open circuit voltage (V oc) of the PSCs.

Lyotropic Liquid Crystal Electrochemical Polymerization of Thiophene-Based Monomers: Polymerization in Cholesteric Liquid Crystal and Columnar Phase

Synthesis of conductive polymer poly([thiophene]-[benzo[1,2,3]thiadiazole] [thiophene]) (abbreviated as P(T-Btdaz-T)) was achieved by electrochemical polymerization in hydroxypropyl cellulose (HPC)/N,N-dimethylformamide (DMF) in liquid crystal state. The polymer thus obtained shows fingerprint texture, which is derived from helical structure of the HPC in cholesteric liquid crystal state. Fourier transform infrared spectroscopy measurements revealed that the polymer film is P(T-Btdaz-T)/HPC composite. Circular dichroism optical absorption spectroscopy measurements show that the polymer has the optical activity. Next, electrochemical polymerization of 3,4-ethylene-dioxythiophene (EDOT) was carried out in columnar phase liquid crystal. The polymer transcribes the columnar structure and shows optical structure resembling columnar liquid crystal electrolyte solution.

The effect of counterion in polymer sulfonates on the synthesis and properties of poly-3,4-ethylenedioxythiophene

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) in the presence of the salt and acid forms of polymer sulfonates with different polymer-chain flexibility is studied. The dependence of the rate of synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) on the nature of polysulfonate counterion that determines the type and distribution density of the charge in the polyelectrolyte chain is demonstrated. For the Н+ form of a rigid-chain polysulfonate, it is found that the specific interactions between parts of its macromolecules lead to destabilization of EDOT•+ radical cations, hinder the growth of PEDOT chains, and favor the formation of structures with the high degree of charge localization.

Morphology and conductivity of PEDOT layers produced by different electrochemical routes

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) in a polyanion, sodium poly(styrene-4-sulfonate)(NaPSS), has been performed through three different oxidative electropolymerizations on flexible electrodes. These electrodes have been fully characterized both at a macroscopic and microscopic scale. The morphology, characterized by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) reveals a tendency of PEDOT:PSS to arrange in cauliflower-like shape. Homogeneity, grain dimension and electrical properties of the PEDOT layers can be tuned by choosing different polymerization routes and different parameters of electropolymerization. At the macroscopic level, we achieved a significant decrease of the impedance of the whole electrode after the electropolymerization thanks to an increase of both the intrinsic conductivity and the roughness of the electrode surface. Moreover Conductive Atomic Force Microscopy (C-AFM) study shows for the first time a clear relation between surface topography and local conductivity of the deposed film and help to clarify the conduction mechanism in electrodeposited PEDOT:PSS layers. The deposition was also shown to be very stable and resistant through thermal accelerated ageing tests that can mimic the behaviour of an implanted electrode after several months at human body temperature. The long term stability coupled with the low impedance make these electrodes suitable candidates for long-term neural probe applications.

In situ scanning tunneling microscopy imaging of electropolymerized poly(3,4-ethylenedioxythiophene) on an iodine-modified Au(1 1 1) single crystal electrode

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on an iodine-modified Au(1 1 1) single crystal electrode in aqueous 0.10 M HClO 4 was investigated by cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (EC-STM). The cyclic voltammetric and EC-STM data revealed the stability of the iodine adlayer provided a suitable potential range for EDOT electropolymerization was controlled at 1.20 V (vs. the reversible hydrogen electrode). EC-STM was used to examine the formation of the PEDOT adlayer on the iodine-modified Au(1 1 1) electrode. In situ electropolymerization of EDOT was carried out by slowly increasing the electrode potential to 1.20 V. This process resulted in the formation of single molecular chains of PEDOT with a diameter of 0.90 nm and lengths of 5–7 nm. Higher resolution STM images further revealed PEDOT nanostructures with bent polymer backbones at angles of 105°, 144° and 180°. The growth of PEDOT multi-layers was observed when the potential was held for a longer time.

Electrochemistry of Conductive Polymers 48. Electrochemical Polymerization of 3,4-Ethylenedioxythiophene in Ionic Liquids and Propylene Carbonate

Systematic studies on the electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) were conducted at gold electrodes in two room temperature ionic liquids (RTILs) sharing the 1-butyl-3-methylimidazolium cation (BMIM+) for one of two anions, BF4 − or TFSI− [bis(trifluoro-methylsulfonyl) imide], and in propylene carbonate (PC) containing BF4 − or TFSI− for a common t-butylammonium cation. EDOT oxidation in RTILs was shown to undergo a change in charge-transfer mechanism during the potential sweep, which must have led to differences in polymerization reactions in the two media. Differences were noted between poly-EDOT (PEDOT) films prepared in RTILs and those in PC; PEDOT films were characterized using techniques including UV-visible absorption spectroscopic, scanning electron microscopic, and Fourier transform electrochemical impedance spectroscopic experiments. The films prepared in PC and with TFSI− displayed the better electrochemical properties. Differences in electron and mass transfer kinetics in different media led to differences observed for film growth kinetics, chain lengths, and redox characteristics for the PEDOT films. Also revealed was that different oxidation mechanisms are at work in RTILs in different potential regimes.

One-step synthesis of polymer-stabilized Ag particles on PEDOT: Effects of stabilizer and electrochemical method on formation of Ag particle

Composites of poly(3,4-ethylenedioxythiophene) (PEDOT) and Ag particles were prepared by electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) and the simultaneous electrochemical reduction of AgNO3 in the presence of poly(vinyl pyrrolidone) (PVP) as a stabilizer. The formation of Ag particles with PVP of various molecular weights and an electrochemical method was investigated. When the high PVP molecular weight was added to the Ag/PEDOT film, the average size of the Ag particles was high. Homogenous spherical Ag particles were observed when cyclic voltammetry was used in the reaction system, whereas chronoamperometry revealed aggregated Ag particles. UV-visible spectroscopy revealed the synchronized formation of Ag particles and PEDOT. The morphology and dispersion of the Ag particles in PEDOT were characterized by scanning electron microscopy. These results suggest that well dispersed homogenous Ag particles can be obtained by applying the proper electrochemical methods or by selecting the optimum PVP molecular weight.

Molecular Assembly and Electropolymerization of 3,4-Ethylenedioxythiophene on Au(111) Single Crystal Electrode as Probed by In Situ Electrochemical STM in 0.10 M HClO4

We have used electrochemical scanning tunneling microscopy (EC-STM) to obtain molecular insights on the adlayer structures and electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on a bare Au(111) single crystal electrode in 0.1 M HClO(4) solution. Cyclic voltammetric (CV) studies showed an increase in anodic current at 0.90 V with the oxidation of EDOT monomer occurring at E = 1.10 V (vs reversible hydrogen electrode). In situ STM revealed, for the first time, that EDOT molecules can spontaneously form organized adlayers on a bare Au(111) surface with 18 muM concentration of EDOT in aqueous solution. Molecularly resolved STM images of the EDOT adlayer showed two domains consisting of disordered and ordered structures with the formation of vacancy islands or "etch pits". Several EDOT structures were observed at +0.60 V, namely, (4 x 7), (5 x square root(37)), and (square root(7) x 3) with calculated coverages of 0.107, 0.114, and 0.111 ML, respectively. Electropolymerization was also carried out using in situ STM in 0.10 M HClO(4) under potential control.

PET fabric/poly(3,4-ethylenedioxythiophene) composite as polymer electrode in redox supercapacitor

Poly(ethylene terephthalate) (PET) fabric/poly(3,4-ethylenedioxythiophene) (PEDOT) composite with stable and high electrochemical activity was fabricated by chemical and electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) on a PET fabric in sequence. Effects of polymerization conditions on the following characteristics of the composite were studied: electrical conductivity and surface morphology. The electrochemical properties were also investigated by cyclic voltammetry and cyclic charge/discharge experiments. The specific volume resistivity, electrical conductivity and specific discharge capacitance of the composite were 0.034 Ω-cm and 25 S/cm, and 54.5 F/g, respectively.

Growth mechanisms, morphology, and electroactivity of PEDOT layers produced by electrochemical routes in aqueous medium

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) in sodium poly(styrene-4-sulfonate) (NaPSS) polyelectrolyte aqueous solution was studied in order to establish a direct relationship between the synthesis conditions and the growth mechanisms of the polymeric film. The final morphology, the polymer structure and the electroactivity of the produced PEDOT:PSS layers have also been investigated in order to achieve a comprehensive understanding of the physico-chemical properties of the material. At this aim the current–time transients referred to the growth best conditions have been fitted using a mathematical equation that considers two contributions corresponding to 3D progressive nucleation under diffusion control and to 3D instantaneous nucleation controlled by charge transfers. The atomic force microscopy study performed on the polymeric films at various stages of electrodeposition supported the proposed growth model. The structural feature and the electrochemical performance of the PEDOT:PSS systems have been studied by Raman spectroscopy and cyclic voltammetry. These studies showed that the adopted experimental conditions allow one to grow PEDOT:PSS films in their oxidized state and characterized by high-capacitive properties.

Optically Active Electrochromism of Poly(3,4-ethylenedioxythiophene) Synthesized by Electrochemical Polymerization in Lyotropic Liquid Crystal of Hydroxypropyl Cellulose/Water: Active Control of Optical Activity

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) in a water solution of hydroxypropyl cellulose (HPC) as a polymer lyotropic liquid crystal (LC) gives polyEDOT*/HPC hybrid (PEDOT*/HPC) as an optically active polymer. Circular differential interference contrast (C-DIC) microscopy of the polymer reveals a well-resolved ordered structure, and circular dichroism (CD) measurements indicate a Cotton effect for the polymer film. PEDOT prepared using this chiral nematic LC field exhibits good electrochemical stability and switching between a dark blue reduced state and sky blue oxidized state with corresponding changes in Cotton effect. The polymer thus shows “electrochiroptical effect”, such as optically active electrochromism, and repeating change in CD through electrochemical redox process. The proposed method represents a new technique for the preparation of chiral conducting polymer films.

Facile design of poly(3,4-ethylenedioxythiophene)-tris(2,2′-bipyridine)ruthenium (II) composite film suitable for a three-dimensional light-harvesting system

It has been confirmed that octasulfonatocalix[8]arene (Calx-S8) and tris(2,2′-bipyridine)ruthenium (II) (Ru(bpy) 3 2+) can form a stable host–guest complex in aqueous solution. The binding constant for 1:1 [Calx-S8 8−·Ru(bpy) 3 2+] 6− complex formation was estimated to be (2.4±0.8)×10 4 dm 3 mol −1 by fluorescence titration, which indicates that the [Calx-S8 8−·Ru(bpy) 3 2+] 6− complex is the main species in 1:1 molar ratio aqueous solution of Calx-S8 and Ru(bpy) 3 2+. In situ UV–Vis spectroscopic measurements indicated that Ru(bpy) 3 2+ complexes can be readily deposited onto ITO electrode through electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) using [Calx-S8 8−·Ru(bpy) 3 2+] 6− host–guest complex as a dopant anion owing to the electrostatic interaction between the cationic conductive polymer and the anionic host–guest complex. The loading degree of the composite film with Ru(bpy) 3 2+ can be determined by Lambert-Beer law modified for the two-dimensional concentration. The obtained composite film showed good photoelectric conversion properties in response to visible light irradiation. This is a novel photocurrent generation system in which the photoexcited state energy is efficiently collected by the conductive polymeric layer.

Anodic polymerization of 3,4-ethylenedioxythiophene from aqueous microemulsions

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDT) was studied in microemulsions containing polyoxyethylene-10-laurylether as a non-ionic micellar surfactant. This allows to increase the solubility of the monomer in an aqueous solution. Thereby, the surfactant affects the transport of EDT. Capacity measurements and cyclic voltammetry on bare Pt show the influence of the surfactant by adsorption on the metal, too. An adsorption on the polyethylenedioxythiophene (PEDT) surface could not be proved. Combined charge transfer and diffusion limitations control the electropolymerization kinetics at low monomer and surfactant concentrations. Charge transfer becomes limiting at high EDT concentrations. Apparent diffusion coefficients and the charge transfer coefficient of the electrochemical reaction were obtained from RDE experiments. The redox activity, UV/VIS spectra and surface morphology (from SEM pictures) depend on the polymerization potential and the solution composition. Best films were obtained at low potentials in LiClO 4. At high potentials overoxidation of the polymer takes place, but an incorporation of the surfactant could not be detected.

In situ ftir spectroelectrochemical characterization of poly(3,4-ethylenedioxythiophene) films

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) and the redox behavior of poly(3,4-ethylenedioxythiophene) (PEDOT) were studied using electrochemical techniques and in situ internal reflection FTIR spectroscopy. A comparison of the IR spectra of PEDOT films taken during charging and discharging in different electrolytes is reported.

In situ spectroelectrochemical characterization of poly(3,4-ethylenedioxythiophene)

The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT), in different electrolyte–solvent media was studied with cyclic voltammetry, in situ UV–VIS-spectroelectrochemistry, electrochemical quartz crystal microbalance technique (EQCM) and with in situ Fourier transform infrared (FTIR) spectroscopy using external and internal reflection techniques. The effect of polymerization current density and monomer concentration on the formation of the film structure was studied. The redox reactions and the stability of charged films of different thickness were studied with cyclic voltammetry and open circuit potentiometric measurements. FTIR spectra were recorded in situ during step-wise and continuous potential cycling of the polymer films in different electrolytes. A characterization of the doping induced IR-bands has been made.

Mechanical, electrochemical and optical properties of poly(3,4-ethylenedioxythiophene)/sulfated poly(β-hydroxyethers) composite films

Poly(3,4-ethylenedioxythiophene)/sulfated poly(β-hydroxyethers) (PEDT/S-PHE) composite films were prepared by electrochemical polymerization of 3,4-ethylenedioxythiophene (EDT) in the presence of S-PHE poly electrolytes. The sulfate groups of S-PHE play the role of the counterion to the positive charges of the oxidized PEDT. Moreover, as a consequence of the good mechanical properties imparted by S-PHE we succeeded in preparing free-standing PEDT composite films. All composites showed excellent mechanical properties, high conductivity and reversible electrochromic properties. In order to examine the influence of the S-PHE content on composite properties, a series of composites containing S-PHEs of differing molar ratios (MR) of sulfate groups to the monomer units of poly(β-hydroxyethers) were synthesized. From the experimental results it was found that the conductivity of the composites is independent of MR value and, hence, PEDT content. In situ absorption spectra of the composite films suggested that composites with larger contents of PEDT possessed shorter π-conjugation lengths. Electrochemical properties of the composites were measured by means of cyclic voltammetry and potential step chronocoulometry and results demonstrated that the rate of switching between the doped and undoped states of the composites occurs within 0.5 s. The absorption band of the composites in the visible region almost disappeared upon doping. All results indicate that the composites are interesting candidates as materials for electrochromic displays.

Synthesis of free-standing poly(3,4-ethylenedioxythiophene) conducting polymer films on a pilot scale

Electrochemical polymerization of 3,4-ethylenedioxythiophene (EDT) was carried out in the presence of monomeric anions or polyanions in electrolyte solutions. While no free-standing films of poly (3,4-ethylenedioxythiophene) (PEDT) were obtained using monomeric anions as dopants, flexible conducting polymers were obtained using novel polyanions, e.g., sulfated poly(β-hydroxyethers) (S-PHE), sulfated poly(β-hydroxyethers) having trifluoromethyl groups (S-PHEF), and sulfated polybutadiene (S-PBD). The conductivity of these PEDT/ polyanion composites exceeded 150 S/cm, and reached as high as 400 S/cm when S-PHEF was used as dopant. These conducting composites demonstrated superior mechanical properties, and PEDT/S-PBD showed an elongation of 78–110% at 100 °C. The electrical properties were strongly dependent on the synthesis conditions. The important parameters were optimized for the S-PHE polyanion. By doing this the conductivity of the PEDT/S-PHE composite reached values around 230 S/cm. Based on the optimized parameters, a continuous synthesis of PEDT/S-PHE composite was developed leading to reproducible conducting composites. The electrode is cylindrical and 10 cm wide. The computer-controlled system enabled the preparation of PEDT films more than 20 m long.