A theoretical study on the interaction between N-methylpyrrole and 3,4-ethylenedioxythiophene units in copolymer molecules

Quantum mechanical calculations at the density functional theory level have been used to examine the interaction between 3,4-ethylenedioxythiophene and N-methylpyrrole units when they are directly linked in copolymer chains. Specifically, in this study, which was motivated by experimental observations of electrochemically synthesized copolymers, the conformation and electronic properties of co-oligomers formed by two, three and four units have been examined in both neutral and radical cation states. Results reveal significant differences, especially in the radical cation state, between the co-oligomers and the corresponding individual homo-oligomers, which have also been explored considering the same theoretical method. Furthermore, electronic properties of oligomers have been used to estimate those of poly(3,4-ethylenedioxythiophene), poly(N-methylpyrrole) and the copolymer with alternated structure, which have been compared among them. The overall results allowed to understand the anomalous features detected in copolymers prepared by electrochemical techniques from 3,4-ethylenedioxythiophene and N-methylpyrrole mixtures, which were initially attributed to some type of unfavourable interaction between the two types of monomeric units.     

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.     

Achieving efficient poly(3,4-ethylenedioxythiophene)-based supercapacitors by controlling the polymerization kinetics

In this study, we have prepared a series of poly(3,4-ethylenedioxythiophene) (PEDOT) with various molecular weight by using an inhibitor, imidazole (Im). The X-ray diffraction (XRD) results show that the PEDOT with larger molecular weight enhances the polymer chain ordering and stacking which leads to higher conductivity. With increasing the amount of Im, the conductivity of PEDOT can be increased from 4.01 S cm⁻¹ (Im = 0.0 M) to 153.6 S cm⁻¹ (Im = 1.8 M). Comparisons of the cyclic voltammetry (CV), it enables correlation between the conductivity and specific capacitance, which is important for understanding the electrochemical capacitive behavior of conjugated polymer for pseudo-capacitor application. The PEDOT prepared with 1.8 M Im shows a specific capacitance of 124 F g⁻¹, which is 2.2 times larger than the one without Im (57 F g⁻¹).     

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.     

Poly(Δ-dicyclopenta[2,1-b:3,4-b′]dithiophene-co-3,4-ethylenedioxythiophene): Electrochemically generated low band gap conducting copolymers

A low HOMO-LUMO gap, alkene bridged bis-bithiophene (Δ^4,4′-dicyclopenta [2,1-b:3,4-b′]dithiophene) has been copolymerized with electron rich 3,4-ethylenedioxythiophene, to produce copolymers with reduced band gaps and enhanced conductivities. Electrochemical band gaps as low as 0.1 eV have been observed, but maximum conductivities were only ca. 0.3 mS cm⁻¹. Poor matching of the HOMO energies of the two components, together with cross-conjugation at the alkene bridge appear to limit charge carrier mobilities. These results provide further evidence that the use of donor and acceptor moieties to decrease band gaps leads to materials with decreased charge carrier mobilities due to charge localization.     

Quantitative in-situ EPR spectroelectrochemical studies of doping processes in poly(3,4-alkylenedioxythiophene)s: Part 1: PEDOT

Quantitative in-situ EPR spectroelectrochemical studies of poly(3,4-ethylenedioxythiophene) (PEDOT) have been carried out with an aim to gain new insights into the doping processes taking place in this polymer. Corroborating the findings made during previous studies of this polymer, absolute measurements conducted in this study provided new detailed information regarding some of the basic parameters characterising the doping process of this conjugated polymer. It was found that concentrations of paramagnetic centres in PEDOT vary from 0.02 spin per mer in the dedoped state up to a maximum of 0.12 spin per mer at 0.15 [e⁻/mer] doping level, corresponding to 1 spin per ca. 8.5 meric units. Such notable concentration values indicate that polarons represent a numerous charge carrier group in PEDOT, contrary to observations made for other members of polythiophene family. Furthermore polarons do not disappear at high doping levels of PEDOT but rather decrease their numbers gradually down to 0.08 spins per mer at a maximum doping level of 0.55 [e⁻/mer] attained in this study. Based on information about concentrations of spins and polymer doping charges, concentrations of bipolarons have been evaluated as a function of doping level. Results indicate that bipolaron formation starts at ca. 0.06 [e⁻/mer] doping level when spin generation efficiency begins to deviate from 1 and interspin interactions emerge as evidenced by doping level dependency of EPR signal linewidth (ΔB_pp). Decomposition of complex EPR spectra of PEDOT in its doped state corroborated the presence of two groups of paramagnetic centres in this polymer. Based upon doping level dependencies of their spectroscopic parameters (concentration, ΔB_pp linewidth and g-factor), the identity of these centres has been redefined compared to our previous reports, linking their properties with the type of polymer phase (crystalline or amorphous) they reside in.     

Structural, chemical and electrochemical characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) prepared with various counter-ions and heat treatments

Electrochemical deposition of the conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT) forms thin, conductive films that are especially suitable for charge transfer at the tissue-electrode interface of neural implants. For this study, the effects of counter-ion choice and annealing parameters on the electrical and structural properties of PEDOT were investigated. Films were polymerized with various organic and inorganic counter-ions. Studies of crystalline order were conducted via X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the electrical properties of these films. X-ray photoelectron spectroscopy (XPS) was used to investigate surface chemistry of PEDOT films. The results of XRD experiments showed that films polymerized with certain small counter-ions have a regular structure with strong (100) edge-to-edge correlations of PEDOT chains at ∼1.3 nm. After annealing at 170 °C for 1 h, the XRD peaks attributed to PEDOT disappeared. PEDOT polymerized with LiClO₄ as a counter-ion showed improved impedance and charge storage capacity after annealing at 160 °C.     

Charging/discharging kinetics of poly(3,4-ethylenedioxythiophene) in 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ionic liquid under galvanostatic conditions

The constant current charging/discharging experiments of poly(3,4-ethylenedioxythiophene) (PEDOT), modified electrodes in room temperature ionic liquid, for instance 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide, were performed for two types of cell configurations, three and two-electrode cells. In each case, a linear variation of the voltage with respect to time was observed. The electrochemical responses were analyzed in term of a series combination of a resistance R and a capacitor C. Accordingly, the capacitance of the modified electrodes was determined. One observed a linear variation of the capacitance as a function of the amount of PEDOT. This capacitance described the chemical capacitance of PEDOT that reflected the capability of the system to accept or release additional charge carriers on a given variation of the chemical potential. Also, the electrochemical response during constant current charging/discharging experiments for two-electrode cell in which the same amount of PEDOT was deposited on each electrode showed a type I electrochemical supercapacitor response. This kind of an electrochemical chain allowed us to mimic and to analyze the electrical responses of an electrochemical actuator based on an interpenetrating polymer networks containing PEDOT that was able to work in air.     

Electrochemical, spectroscopic and electrogravimetric detection of oligomers occluded in electrochemically synthesized poly(3,4-ethylenedioxythiophene) films

This paper shows that oligomers are retained inside the polymer film during the electrosynthesis of poly(3,4-ethylenedioxythiophene), PEDOT, in aqueous media. The behavior of the electrochemically generated PEDOT film is highly dependent on the presence of these oligomers. A detailed study of the release of oligomers trapped in the PEDOT film has been carried out using bidimensional spectroelectrochemistry (BSEC), spectroelectrochemical quartz crystal microbalance (SEQCM) and scanning electrochemical microscopy (SECM). These multiresponse techniques have allowed us to determine when these EDOT oligomers are released into solution and to investigate their electrochromic properties. Mass spectroscopy measurements revealed that most of these oligomers consist of four or six monomer units, which seem to be the most stable species in aqueous solution.     

Flexible electrochromic device based on poly (3,4-(2,2-dimethylpropylenedioxy)thiophene)

In this study, the design, fabrication and characterization of a flexible electrochromic device based on indium tin oxide (ITO) coated polyethylene terephthalate (PET) plastic is discussed. The working electrochromic material film was poly (3,4-(2,2-dimethylpropylenedioxy)thiophene) (PProDOT-Me₂), while the counter layer of the device was vanadium oxide titanium oxide (V₂O₅/TiO₂) composite film, which serves as an ion storage layer. A solution type electrolyte was used as the ionic transport layer and was sandwiched between the working and counter layers. The device exhibited tuneable light transmittance between transparent and deep blue color, with a maximum contrast ratio at 580 nm wavelength. Other important properties, such as switching speed, life time, and coloration efficiency have been improved.     

Accumulation of Cu(II) cations in poly(3,4-ethylenedioxythiophene) films doped by hexacyanoferrate anions and its application in Cu-selective electrodes with PVC based membranes

Electrochemical properties of poly(3,4-ethylenedioxythiophene) doped with hexacyanoferrate(II,III) ions (PEDOT(HCF)) were studied in the presence of Cu²⁺ ions. Voltammetric and EDAX studies revealed retention of hexacyanoferrate anions in the polymer film and accumulation of Cu(II) cations, as well as formation of solid copper hexacyanoferrate near the polymer surface.Accumulation of Cu²⁺ ions was found to be advantageous from the point of view of PEDOT(HCF) applications as a solid contact (ion-to-electron transducer) in all-solid-state Cu²⁺-selective electrodes with solvent polymeric polyvinyl chloride (PVC) based membrane, containing Cu²⁺-selective ionophore. Binding of Cu²⁺ ions in the conducting polymer layer results in analyte ions flux into the transducer phase. Thus, pronounced enhancement of selectivity of the all-solid-state Cu²⁺-selective electrode or lower detection limit of the potentiometric response range was achieved, reaching under optimised conditions 10⁻⁷ M CuSO₄.     

Chemical cross-linking of conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using poly(ethylene oxide) (PEO)

Hybrid films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were prepared with different molecular weights of poly(ethylene oxide) (PEO). The cross-linking reaction between PEO and PEDOT:PSS was performed at high temperature and confirmed by using differential scanning calorimeter (DSC), contact angle measurement, and solid-state ¹H NMR. The effect of chemical reaction on the conductivity and morphology of these hybrid films was studied by using 4-point probe and atomic force microscope (AFM), respectively. As-spun PEO/PEDOT:PSS films have lower electric conductivity due to the addition of nonconductive PEO, and exhibits no molecular weight dependence on conductivity. After chemical cross-linking reaction at high temperature, only PEDOT:PSS films with lowest molecular weight PEO additives show enhanced conductivity with increasing reaction time. AFM result indicates that the heat-treated PEO/PEDOT:PSS hybrid films show grain-like morphology compared to ethylene glycol treated PEDOT:PSS films which shows continuous PEDOT domain. In the present work we demonstrate that the cross-linking reaction can be used to improve the wet stability of PEDOT:PSS nanofiber, showing good water resistance and excellent dimensional stability.     

Facile synthesis and light scattering characteristics of polystyrene/poly(3,4-ethylenedioxythiophene) nanocomposite particles

Polystyrene/poly(3,4-ethylenedioxythiophene) (PS/PEDOT) nanocomposite particles with uniform size and well-defined morphology have been synthesized using the proposed strategy, which involves swelling of 3,4-ethylenedioxythiophene (EDOT) into PS seed particles, followed by its diffusion and polymerization on the PS surface. This process affords much more effective control over the structure and morphology of the resultant nanocomposites by changing the EDOT/PS weight ratio, reaction temperature, and the rate of addition of the doping acid. The PS/PEDOT nanocomposite particles have been extensively characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), elemental microanalyses and X-ray photoelectron spectroscopy (XPS). Furthermore, the correlation between nanostructure of the resultant nanocomposite particle and its electromagnetic response performance (e.g., mass extinction effect in infrared region) was investigated.     

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.     

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.     

Integration of vanadium-mixed addenda Dawson heteropolytungstate within poly(3,4-ethylenedioxythiophene) and poly(2,2′-bithiophene) films by electrodeposition from the nonionic micellar aqueous medium

A comparative study describing immobilization of the Dawson type mixed addenda heteropolyanion, [P₂W₁₇VO₆₂]⁸⁻ into conducting polymer films of poly(3,4-ethylenedioxythiophene), PEDOT, and poly(2,2′-bithiophene), PBT, is reported. Electrosynthesis of these hybrid films was performed using a micellar aqueous solution of the nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-100). Deposited composite films were characterised electrochemically and, on the whole, they exhibited fast electron transfer (ET) properties and relatively high stability towards continuous potential cycling in acidic media. In particular, PEDOT composite showed relatively faster ET properties in comparison to PBT composite. Their permeability was investigated in the presence of cationic and anionic redox probes. Our results implied good mediating capabilities of the [P₂W₁₇V⁴⁺O₆₂]⁸⁻ anion (within the [P₂W₁₇V⁴⁺O₆₂]⁸⁻–PEDOT hybrid film) towards the iron (III) reduction. The specific electrocatalytic (reductive) capabilities of hybrid films were also studied by probing the reduction of bromate. The films were further characterised by X-ray photoelectron spectroscopy to establish their interfacial elemental composition. Moreover, their surface morphology was imaged by atomic force microscopy and scanning electron microscopy. Results have shown that physicochemical properties of the investigated hybrid films were affected by polymer hydrophobicity.     

Amphiphilic polythiophene for the formation of gold nanowire networks

Polythiophene containing amphiphilic decyl-tri(oxyethylene) side group was synthesized. Gold nanowire networks having almost uniform wire diameters could be prepared when the amphiphilic polythiophene was mixed with hydrogen tetrachloroaurate (HAuCl₄) in THF followed by the addition of aqueous sodium borohydride solution. The size of nanowire networks and the diameter of the component wires could be controlled by changing the polymer concentration and the gold salt to polymer ratios. When polythiophene derivatives having hydrophobic or hydrophilic side groups were used instead of the amphiphilic polythiophene, disconnected poor networks and coagulated nanoparticle chunks, respectively, were obtained, although the same reduction process was applied.     

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     

On the molecular properties of polyaniline: A comprehensive theoretical study

A comprehensive study about the molecular and electronic properties of the different forms of polyaniline has been developed using quantum mechanical calculations. Initially the performance of different ab initio and DFT quantum mechanical methods has been evaluated by comparing the results provided for small model compounds containing two repeating units. After this, calculations on the emeraldine base, leucoemeraldine base, pernigraniline base and emeraldine salt (monocationic and dicationic) forms of oligoanilines with n repeating units, where n ranged from 5 to 13, have been performed using the BH&H/6-31G(d) method, which was found to be a very suitable theoretical procedure. Interestingly, calculations indicate that the distribution in blocks of the repeating units containing amine and imine nitrogen is largely preferred for the emeraldine base form. On the other hand, the molecular structure and band gap of the emeraldine base, leucoemeraldine base and pernigraniline base forms have been rationalized according to their differences in the conjugation of the C₆H₄ rings. Calculations on cationic oligoanilines indicate that, when the emeraldine salt form presents a doublet electronic state, the positive charge and the spin density are located in the middle of the chain extending through five consecutive repeating units.