EQCM and in situ conductance studies on the polymerisation and redox features of thiophene co-polymers (original) (raw)
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Synthetic Metals, 1986
Passive, ultra-thin dielectric films (5-7 nm) of poly(phenylene oxide), PPO, are formed by the anodic electropolymerization of tetramethylammonium phenoxide from acetonitrile onto Pt or Au electrodes. These films can have exceptionally low permeabilities to solution redox species, depending on electrcpolymerization potential, the time of deposition, and cross-linking reactions. The latter becomes evident at +0.4 V vs. SSCE and in the presence of electrogenerated mediator-oxidant. PPO blocks the cyclic voltammetry of ferrocene carboxylic acid and Cl-oxidations in acetonitrile by > 99% and 922, respectively, and reduction of [Fe(CN)JM3 and oxidation of the sodium salt of ferrocene carboxylic acid in water by > 99%. By rotating disk voltammetry, the permeability PDs.poL of the film to FeCp,* in CH,CN is as low as 8 x lo-" cm2/s. Films prepared from alkyl substituted phenolates are thicker, more hydrophobic, but also more permeable owing to less efficient cross-linking. Film thicknesses were obtained by profilometry, ellipsometry, XPS, and high frequency electrical capacitance measurements, and physical and structural information by use of contact angle measurements and attenuated total reflectance FTIR.
Journal of Solid State Electrochemistry, 2007
A new oligomer of N,N′-bis(2-pyrrolyl methylene)-3,4-dicyano-2,5-diaminothiophene possessing cyanosubstituted thiophene and pyrrole residues linked together by azomethine groups was used for the electrochemical polymerisation of conducting films. The approach used for the oligomer design favours inter-chain interactions through hydrogen bonding and negative charge stability through the cyano substitute thiophene. The oligomer was successfully electropolymerised at 0.67 V vs Ag + /Ag from 0.1M tetrabutylammonium tetrafluoroborate (TBABF 4 )/acetonitrile as a dark blue film on the surface of platinum electrodes. Cyclic voltammetry has been used to investigate the redox behaviour of the films. The electrically conducting polymer showed p-doping/neutralisation behaviour. The effect of different electrolytes such as TBABF 4 , tetrabutylammonium perchlorate (TBAClO 4 ), lithium perchlorate (LiClO 4 ) and sodium perchlorate (NaClO 4 ) on the redox switching and the stability of the polymer films was investigated. Infrared and UV-vis spectra of oligomer and polymers are presented. The evolution of the film growing process is shown by UV-vis spectroscopy.
Electrochimica Acta, 2000
Poly(3-dodecylthiophene) films were synthesised electrochemically from a propylene carbonate solution of the monomer, by galvanostatic method and cyclic voltammetry. Electrochemical properties of the resulting polymers were compared with the properties of regioregular head-to-tail (HT) polymer synthesised chemically. The first part of the work is focused on the electrochemical characteristics of HT polymer, namely on dependence of the shape of cyclic voltammograms obtained for redox reaction of the polymer on the film thickness and mean conjugation length. In the second part, the optimum conditions of electrosynthesis have been established. The quartz crystal microbalance measurements carried out during potentiodynamic polymerisation of 3-dodecylthiophene (by cyclic voltammetry) showed that deposition of the polymer film was preceded by dissolution of the gold substrate. At the later stage of the film formation, the oligomers that were initially accumulated in the vicinity of the electrode, attained the crucial lengths and precipitated on the electrode surface. In the case of a slow diffusion of the monomer to the electrode the growing film may be irreversibly overoxidised or/and crosslinked.
Synthetic Metals, 1997
The copolymers poly(3-methylthiophene-co-3,4-ethylenedioxythiophene) were prepared from mixtures of 3-methylthiophene and 3,4-ethylenedioxythiophene via electrochemical oxidation. Various concentrations of the monomers in the mixture at a fixed polymerization potential, or fixed concentrations of the monomers in the mixture at various polymerization potentials were used to produce copolymers. Electrochemical and spectroscopic characterizations demonstrate the possibility of modulating continuously the electrochemical and optical properties of the individual polymers.
Electrochemical and electrochromic response of poly(thiophene-3-acetic acid) films
Solar Energy Materials and Solar Cells, 2004
Thiophene-3-acetic acid has been polymerized in chloroform by a chemical method using FeCl3 as oxidant. The films were prepared casting the solubilized polymer on ITO electrodes and studied using cyclic voltammetry, chronoamperometry and spectroelectrochemistry. During the potential sweep, an electrochromic process is observed in which the film color changes from red to black. High electrochromic efficiency was observed for more than 600 cycles, although it decreases to 73% of the initial value. Until 264 cycles, the electrochromic efficiency at 750 nm is stable and the value is 242 cm2 C−1.
Theoretical Treatment of 3-Phenylsubstituted Thiophenes and Their Intrinsically Conducting Polymers
ECS Transactions, 2007
A series of 3-(p-X-phenyl) thiophene monomers (X= -H, -CH3, - OCH3, -COOC2H5, -COCH3,-NO2) was electrochemically polym-erized to furnish polymer films that could be reversibly reduced and oxidized (n- and p-doped). The oxidation potentials of the monomers and formal potentials of the n- and p-doping processes of polymers were correlated with resonance and inductive effects of the substituents on the phenyl ring as well as the semiempirically calculated heats of formation of the monomer radical cations. Moreover, the oxidation potentials of the monomers were correlated with the ionization potentials of the monomers calculated using density functional theory. The reactivity for coupling reactions and the major regioselective products of the polymerization reaction of mono- and oligo-3- phenylthiophenes are inferred from the calculated lone electron spin densities of the respective radical cations. The ionization potentials, which correspond to the energies for generating radical catio...
Electrochimica Acta, 2003
Poly(3,4-dialkoxythiophene) films with different length of alkyl chain (1,3 and 8 carbon atoms) were obtained on Pt and ITO electrodes from the monomer solutions in acetonitrile by cyclic voltammetry (CV). The properties of the resulting films were studied by electrochemical methods, UV Á/Vis, FTIR and NMR spectra. The CVs were correlated with differential cyclic voltabsorptograms (DCVA) recorded at the absorption maxima to explain the shape of the voltammograms of the polymers studied, dependent on the alkyl-chain length in alkoxy group. The presence of the zones of different crystallinity in the polymer film was postulated. Significant influence of the type of the solvent on asymmetry of the cyclic voltammograms for the polymer doping Á/undoping has been discussed in terms of the solvent interaction with radical cation (polaron) delocalized on the alkoxy side groups. The polaron delocalization was proved by 1 H-NMR spectra. Appearance of infrared activated vibrations (IRAVs) in the range 1500 Á/600 cm (1 and a characteristic electronic band at 3300 cm (1 at the polarization potential '/0.25 V versus Ag/Ag ' and their gradual changes upon further polymer oxidation were interpreted in terms of evolution of different charge carriers in lightly and heavily doped polymer. #
Electrochemical Copolymerization of Thiophene Containing Pseudo-Polyether Cages with Pyrrole
2006
Conducting copolymers were synthesized via the electrochemical oxidation of pyrrole (Py) in the presence of the monomer 1,12-bis(2-thienyl)-2,5,8,11-tetraoxadodecane (I). The presence of monomer I in the electrolytic solution greatly changed the CV behavior of Py during its potensiodynamic polymerization. The electroactivity of poly(I-co-Py) increased with the increasing amount of I in the comonomer mixture. Copolymer films were prepared via constant potential electrolysis in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) dissolved in acetonitrile. The spectroelectrochemical properties of the films were investigated using UV-VIS spectroscopy.
Electrochemical copolymerization of thiophene derivatives; a precursor to photovoltaic devices
Electrochimica Acta, 2011
This work presents an electrochemical technique for the polymerization and copolymerization of thiophene derivatives like 7,9-dithiophene-2yl-8H-cyclopenta[a]acenaphthalene-8-one and 3-hexylthiophene. The structural characterization of chemically synthesized monomers and electrochemically synthesized polymers was carried out by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Thermal characterizations indicate that copolymer has increased thermal stability than that of homopolymer. Morphological studies of the polymerized films carried out by scanning electron microscopy shows network structure of copolymer. Optical properties of the homopolymers and copolymer were studied by UV-visible spectrometer and it was observed that band gap of copolymer is less than the homopolymers. HOMO and LUMO levels, band gap values of the respective polymers were also calculated from the cyclic voltammetry technique with various scan rates. By the peak current obtained from various scan rates shows that all polymerization reactions are diffusion controlled process. Charge transfer resistances of polymers were determined using Nyquist plots. Conductivity of synthesized polymers shows higher conductivity for copolymer than homopolymers.