Preparation and electrical conductivity of Langmuir–Blodgett films of poly(3-alkylthiophene)s

Five poly(3-alkylthiophene)s (P3ATs) with different alkyl side chains were synthesized. Pure P3ATs alone are not well suited for manipulation by the Langmuir–Blodgett (LB) technique, but their mixed systems with arachidic acid can be used to prepare high-quality Y-type films with the vertical dipping method, which was proved by UV-visible spectra and small-angle X-ray diffraction patterns. Conductivities of the LB films were measured using a two-probe method at room temperature. The conductivities exhibited obvious anisotropy and could increase by 2–4 orders of magnitude after iodine vapor doping. The influence of alkyl chain length on the conductivity in the LB films was revealed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1–6, 1998     

Effect of irradiation on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) nanofiber conductivity

Conducting nanofibers of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polyvinyl alcohol (PEDOT:PSS/PVA) were fabricated at room temperature and via electrospinning with diameters ranging from 100 to 300 nm. The nanofibers were irradiated with Gamma and X-rays for varying lengths of time and the change in conductivity was evaluated. Raman and Electron Spin Resonance spectroscopy of X-ray irradiated nanofibers were obtained to determine the mechanism of conductivity degradation. A decrease in molecular ordering as well as chain scission via chain cross-linking and free radical formation are the two most likely mechanisms for change in conductivity. These nanofibers are promising candidates for use in highly sensitive, real-time electrically based sensor for radiation detection.     

Graphene/poly(3,4-ethylenedioxythiophene) hydrogel with excellent mechanical performance and high conductivity

We report a novel and easy route to synthesize a mechanically strong hydrogel composed of graphene and poly (3,4-ethylenedioxythiophene) (PEDOT). 3,4-Ethylenedioxythiophene played the role of reducing agent to convert a highly oxidative graphite oxide (h-GO) to graphene and in situ polymerized itself synchronously on the active sites of the graphene to construct the hydrogel. The content of the carbonyl groups in h-GO was found to have a major impact on the generation of the hydrogel. Also the morphology and the quantity of PEDOT formed in the hydrogel were considered to be the key factors for improving the mechanical performance of the hydrogel. As-prepared enhanced graphene/PEDOT hydrogel displayed a compressive fracture stress as high as 29.6 MPa, a storage modulus about 2.1 MPa at 10 rad/s, a good electrical conductivity of 0.73 S/cm and a high specific capacitance of 174.4 F/g, which make it a potential candidate for a number of technologies such as electrochemical sensor and supercapacitor.     

Order-disorder transitions in poly(3,4-ethylenedioxythiophene)

The commonly held perception that high conductivity in conducting polymers is linked to a high level of π-stacking order in the material is shown here to be of lesser importance in highly conducting poly(3,4-ethylenedioxythiophene) (PEDT), which has been prepared by chemical vapour phase polymerisation. Despite the fact that there is a highly energetic phase transition about 130 °C (110 J/g), and that this transition corresponds to a loss of the long-range π-stacking as observed in grazing angle XRD, the conductivity remains unchanged beyond the transition and only decreases by a factor of two when heating to above 200 °C. The XRD data suggest that order in two dimension remains above the phase transition measured by DSC and this order is sufficient to maintain a high level of electronic conductivity. Furthermore, as the ligand on the iron salt used in the synthesis is varied, the conductivity of the PEDT varies over two orders of magnitude. These phenomena cannot be explained by different degree of doping or crystallinity and it is proposed that the iron salt has an ordering effect during the vapour phase polymerisation.     

Ultrafast-laser-treated poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) electrodes with enhanced conductivity and transparency for semitransparent perovskite solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is an important organic electrode for solution-processed low-cost electronic devices. However, it requires doping and post-solvent treatment to improve its conductivity, and the chemicals used for such treatments may affect the device fabrication process. In this study, we developed a novel route for exploiting ultrafast lasers (femtosecond and picosecond laser) to simultaneously enhance the conductivity and transparency of PEDOT:PSS films and fabricate patterned solution-processed electrodes for electronic devices. The conductivity of the PEDOT:PSS film was improved by three orders of magnitude (from 3.1 to 1024 S·cm^–1), and high transparency of up to 88.5% (average visible transmittance, AVT) was achieved. Raman and depth-profiling X-ray photoelectron spectroscopy revealed that the oxidation level of PEDOT was enhanced, thereby increasing the carrier concentration. The surface PSS content also decreased, which is beneficial to the carrier mobility, resulting in significantly enhanced electrical conductivity. Further, we fabricated semitransparent perovskite solar cells using the as-made PEDOT:PSS as the transparent top electrodes, and a power conversion efficiency of 7.39% was achieved with 22.63% AVT. Thus, the proposed route for synthesizing conductive and transparent electrodes is promising for vacuum and doping-free electronics.     

On the mechanism of conductivity enhancement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film through solvent treatment

The conductivity of a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film is enhanced by more than 100-folds on adding some organic compounds into PEDOT:PSS aqueous solutions or by treating the PEDOT:PSS film with organic solvents, such as ethylene glycol (EG), 2-nitroethanol, methyl sulfoxide or 1-methyl-2-pyrrolidinone. The mechanism for this conductivity enhancement was studied through various chemical and physical characterizations. The PEDOT:PSS film which is soluble in water becomes insoluble after treatment with EG. This strongly suggests an increased interchain interaction among the PEDOT chains. Raman spectroscopy indicates that this increased interchain interaction results from conformational changes of the PEDOT chains, which change from a coil to linear or expanded-coil structure. The increased interchain interaction and conformation changes are further confirmed by the temperature dependence of conductivity and the electron spin resonance (ESR). It is found that EG treatment lowers the energy barrier for charge hopping among the PEDOT chains, lowers the polaron concentration in the PEDOT:PSS film by ∼50%, and increases the electrochemical activity of the PEDOT:PSS film in NaCl aqueous solution by ∼100%. Atomic force microscopy (AFM) and contact angle measurements show that the surface morphology of the PEDOT:PSS film changes as well after the EG treatment. Conductivity enhancement was also observed when other organic compounds were used, but it was strongly dependent on the chemical structure of the organic compounds, and observed only with organic compound with two or more polar groups. These experimental results support our proposal that the conductivity enhancement is due to the conformational change of the PEDOT chains and the driving force is the interaction between the dipoles of the organic compound and dipoles or charges on the PEDOT chains.     

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.     

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.     

Regioregular poly(3-alkylthiophene) conducting block copolymers

Regioregular poly(3-alkylthiophenes) (PATs) represent an important class of polymers that are environmentally stable and display high electrical conductivity. Despite their excellent electrical properties, PATs do not exhibit very good mechanical and processing properties. This issue is addressed here by integrating poly(3-alkylthiophene) in copolymer structures with various polymer blocks that display better mechanical properties, leading to a variety of polymeric materials with desired properties. We describe a new method for the synthesis of poly(3-alkylthiophene) block copolymers using vinyl terminated regioregular poly(3-alkylthiophene) as precursors via atom transfer radical polymerization (ATRP).     

Synthesis of small-band gap poly(3,4-ethylenedioxythiophene methine)s using acidic ionic liquids as catalyst

Poly(3,4-ethylenedioxythiophene methine)s were synthesized in the presence of acidic ionic liquids for the first time. The polymers were obtained in good yields and viscosities ranging which were soluble in most common solvents such as NMP, THF, CH₂Cl₂, p-dioxane, chloroform, etc. The polymer structures were confirmed by FT-IR, UV–Vis-NIR, ¹H-NMR spectra, elemental and thermogravimetric analysis techniques. The thermal gravimetric analysis showed that the polymers had a fairly good thermal stability. The optical and electrochemical band gaps of the synthesized polymers were 1.16–2.3 and 1.7–2.05 eV, respectively. The electrochemical impedance spectroscopy studies were shown that polymers conductivity was greatly increased after doping of polymers with iodine.     

Electrical conductivity of polymer blends of poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate): N-methyl-2-pyrrolidinone and polyvinyl alcohol

The goal of this study is to determine the electrically conductivity of the polymers poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate): N-methyl-2-pyrrolidinone (PEDOT: PSS: NMP) and PEDOT: PSS when blended with polyvinyl alcohol (PVA). While the conducting polymers have high conductivity when not blended with PVA, they are brittle and difficult to spin-coat. Thus, the motivation for this study is to develop blends of these two conducting polymers with PVA to produce a material with optimized mechanical properties and that can also be spin-coated. The blends are produced using aqueous preparations of these materials. Mixtures of various weight percentages (wt %) of PEDOT: PSS: NMP and PEDOT: PSS are prepared and spin-coated on glass slides to form thin films. In the blends, the film conductivity increases with increasing content of either PEDOT: PSS: NMP or PEDOT: PSS. For example, 100 wt % of PEDOT: PSS: NMP and 60 wt % of PEDOT: PSS: NMP blended with PVA exhibit conductivities of, respectively, 10 and 4.02 S/cm. In contrast, conductivities of only 0.0525 and 0.000506 S/cm are observed, respectively, for 100 wt % of PEDOT: PSS and 60 wt % of PEDOT: PSS content in the PEDOT: PSS/PVA blends (No NMP). The addition of the NMP enhances the electrical conductivity by two to five orders of magnitude (depending on the amount of PVA in the blend) due to conformational change of PEDOT chains. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

Electropolymerization and characterization of COOH-functionalized poly(3,4-ethylenedioxythiophene): Ionic exchanges

The electropolymerization of COOH-functionalized 3,4-ethylenedioxythipohene was investigated by cyclic voltammetry, by anodic potential steps or by flow of a constant anodic current. Compared with PEDOT, an anodic shift of the oxidation polymerization potential is observed. Nevertheless the polymer film oxidation/reduction is shifted to more cathodic potentials, giving higher stored specific charges than those obtained from PEDOT films generated in similar conditions. The generated polymer shows a stable redox process, E⁰ = −0.04 V. EQCM results point to a p-doping process exchanging anions with solution, whereas a second reduction process at −0.77 V is related to a p-doping process exchanging cations. The new material is electrochromic: it is colourless in its oxidized state and blue colour in its reduced state. UV–Vis spectroelectrochemical results are similar to those obtained from PEDOT films.     

Electrochemical characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated thiophenes

Sulfonated thiophenes, sodium 2-(3-thienyloxy)ethanesulfonate (C₆H₇S₂O₄Na) and sodium 6-(3-thienyloxy)hexanesulfonate (C₁₀H₁₅S₂O₄Na), were synthesized and used in the fabrication of ion-selective electrodes (ISEs) sensitive and selective to Ag⁺. The Ag⁺-ISEs were prepared by galvanostatic electropolymerization of 3,4-ethylenedioxythiophene (EDOT) on glassy carbon (GC) electrodes, with either C₆H₇S₂O₄⁻ or C₁₀H₁₅S₂O₄⁻ as the charge compensator (doping ion) for p-doped poly(3,4-ethylenedioxythiophene) (PEDOT). Potentiometric measurements were carried out with these sensors, GC/PEDOT(C₆H₇S₂O₄⁻) and GC/PEDOT(C₁₀H₁₅S₂O₄⁻), to study and compare their sensitivity and selectivity to silver ions. PEDOT(C₆H₇S₂O₄⁻) and PEDOT(C₁₀H₁₅S₂O₄⁻) films were also studied by using other techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), electrochemical quartz crystal microbalance (EQCM) and Fourier transform infrared spectroscopy (FTIR).Results from the potentiometric measurements showed that the difference in length of the alkyl chain of the doping ions C₆H₇S₂O₄⁻ and C₁₀H₁₅S₂O₄⁻ has no significant effect on the sensitivity or selectivity of GC/PEDOT(C₆H₇S₂O₄⁻) and GC/PEDOT(C₁₀H₁₅S₂O₄⁻) sensors to Ag⁺. More differences can be seen in the cyclic voltammograms and EIS spectra of the sensors. FTIR spectra confirmed that both C₆H₇S₂O₄⁻ and C₁₀H₁₅S₂O₄⁻ act as doping ions in the electrosynthesis of PEDOT-based films and they are not irreversibly immobilized in the polymer backbone.     

Recovery and characterization of pure poly(3,4-ethylenedioxythiophene) via biomimetic template polymerization

The fundamental properties of pure poly(3,4-thylenedioxythiophene) (PEDOT), one of the most common electrically conducting organic polymers, are the key to the development of more prominent applications in which PEDOT and its derivatives can be utilized. Conducting molecular complex of PEDOT with silica was synthesized in the presence of charged silica template by the in situ biomimetic polymerization. To remove silica from PEDOT/template complex, hydrofluoric acid was used to etch silica particles. The electrochemical, thermal, and optical properties of pure PEDOT recovered were investigated in comparison with those of EDOT monomer or PEDOT with template by using UV–vis–near–IR spectra, cyclic voltammetry, thermogravimetric analysis, and fluorescence spectra. POLYM. ENG. SCI., 47:71–75, 2007. © 2006 Society of Plastics Engineers     

A comprehensive study of the interactions between DNA and poly(3,4-ethylenedioxythiophene)

The interaction between poly(3,4-ethylenedioxythiophene), a conducting polymer with excellent electrical and electrochemical properties, and plasmid DNA has been investigated using electrophoresis, UV-visible and CD spectroscopy, and quantum mechanical calculations. Analyses of mixtures with different DNA:polymer mass ratios indicate that, in all cases, interactions form immediately and induce structural alterations in DNA. Furthermore, the existence of interactions between poly(3,4-ethylenedioxythiophene) and specific nucleotides sequences has been evidenced by adding restriction enzymes to the mixtures. In contrast, interactions between DNA and poly(3-methylthiophene), a similar polyheterocyclic conducting polymer but without hydrogen bonding acceptors, are weak or do not exist. These results suggest that, in addition to non-specific electrostatic interactions between the charged phosphate groups of DNA and the positively charged fragments of the conducing polymers, specific hydrogen bonding interactions play a crucial role. The ability of 3,4-ethylenedioxythiophene units to form hydrogen bonds with the methylated analogues of DNA bases has been examined in different environments using MP2/6-31G(d) and MP2/6-311++G(d,p) calculations. Results indicate that, in environments with low polarity, the formed interactions are significantly stronger than those reached by unsubstituted thiophene and similar to those established by pyrrole. However, in polar environments (aqueous solution) 3,4-ethylenedioxythiophene provides stronger interactions with nucleic acids than both thiophene and pyrrole. These theoretical results are fully consistent with experimental observations.     

导电聚合物PEDOT/PSS-MPEG的制备及性能

引言导电高分子既有导体材料的光电学特性,又有良好的力学性能和可加工性[1],这使得导电高分子材料具有广泛的应用前景。聚噻吩类有机导电材料[2]就是这类材料中的一种。聚噻吩的室温电导率     

Different steps in the electrosynthesis of poly(3,4-ethylenedioxythiophene) on platinum

The initial stages of poly(3,4-ethylenedioxythiophene) (PEDOTh) film growth on platinum electrodes from TBAClO₄/acetonitrile solution are investigated by means of current-time transient measurements and tapping mode atomic force microscopy. It is shown that, for growth potentials in the range 1.17-1.29 V vs. SCE, the deposition process involves the formation of oligomers in the solution, progressive nucleation of centres of the new phase and three-dimensional growth of a first compact layer followed by a non-uniform distribution of granular-like clusters, whose number and size increase with the synthesis potential and charge. The obtained results reveal that PEDOTh films prepared at distinct potentials but with the same growth charge (Q_g) display similar electroactivities. They also depict that the electrochemical behaviour of the films is a function of the charge used for the synthesis, namely the reduction of tick PEDOTh layers (Q_g > 20 mC cm⁻²) includes more that one step, as a consequence of the formation of a two-layered polymer film.     

Synthesis, electropolymerization and oxidation kinetics of an anthraquinone-functionalized poly(3,4-ethylenedioxythiophene)

The chemical synthesis of an EDOT derivative endowed with an electron acceptor anthraquinone moiety (AQ-EDOT) is described. The electrochemical polymerization of the monomer has been studied by cyclic voltammetry, chronoamperometry and chronopotentiometry. The monomer oxidation-polymerization takes places on platinum at potentials more positive than 1.3 V vs. Ag/AgCl. The polymer film presents a stable redox process with E⁰ = 0.22 V, that can be assigned to the characteristic exchange process of the parent unsubstituted PEDOT polymer. An unstable redox process at E⁰ = −1.00 V, present decreasing charges on the consecutive cycles despite that the lost reduction charge is recovered by two irreversible oxidation processes taking place at high anodic potentials 0.00 and 0.16 V. A structural charge trapping effects occurring by reduction at −1.1 V and re-oxidation at 0.16 V of the anthraquinone moiety is suggested. The stable redox process is not affected by cycling allowing the obtention of the oxidation empirical kinetics, kinetic coefficients and reaction orders. Different initial states attained by reduction at different cathodic potentials for a constant time were explored for the kinetic study.     

Effect of steric hinderance on junction properties of poly (3-alkylthiophene)s based schottky diodes

n -hexylthiophene), and metals, such as, In, Ag, Al, Sn, etc. The polymers were synthesised chemically using ferric chloride as catalyst. The electrical properties of the devices have been studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements. Junction parameters such as ideality factor (n) and barrier height (χ) have been calculated on the basis of thermoionic emission theory. Better performance of P3cHT/metal diode, compared to P3nHT was attributed to the steric effects produced by cyclohexyl unit present in the polymer. Received: 19 May 2000/Accepted: 23 August 2000