High yield preparation of a soluble polyaniline derivative

The effect of pH, temperature, monomer/oxidant molar ratio, catalysts and ionic strength on the reaction yield and electrical conductivity of chemically synthesized poly(o-methoxyaniline) was studied. Based on this, poly(o-methoxyaniline) was prepared in the presence of p-toluene-sulfonic, dodecyl-benzene-sulfonic and dodecylsulfuric acids. Poly(o-methoxyaniline) was obtained with 90% yield and a conductivity of 0.1 S cm(-1) when p-toluene-sulfonic acid was used. The use of functionalized acids increased the thermal stability of the polymer in relation to HCI with no changes in the electric conductivity. The polymer is soluble in common organic solvents, enabling the preparation of films by casting. We also discuss the polymerization kinetics of o-methoxyaniline in the presence of HCI and of the functionalized acids as a function of monomer/oxidant ratio.80326326

THERMAL AND PHOTOCHEMICAL DEGRADATION OF DODECYL-SULFATE DOPED POLYPYRROLE

The authors report on the changes of the electrical, morphological, chemical and electrochemical properties of polypyrrole dodecylsulfate films aged at 100-degrees-C or exposed to a solar simulator light source. The thermal aging induces a loss of conductivity and a gradual decrease of the anodic and cathodic peak currents, as measured by cyclic voltammetry. Irradiation does not substantially alter the properties of the films; the conductivity does not change and the electroactivity is slightly modified. Degradation of the properties is attributed to cross-linking, oxidation and evaporation of low molecular weight oligomers.42331732

Electrochemical, electrochromic and photoelectrochemical behavior of a highly soluble polyaniline derivative: Poly(o-methoxyaniline) doped with functionalized organic acids

Poly(o-methoxyaniline) was chemically prepared in the presence of hydrochloric, p-toluene-sulfonic, dodecyl-benzene-sulfonic or dodecyl-sulfuric acids. Films of this polymer were prepared by casting and electrochemical, electrochromic and photoelectrochemical properties were studied. Cyclic voltammetry experiments show well-defined redox waves when the pH of the electrolyte is 1.0. Poly(o-methoxyaniline) films present high optical contrast in the visible range, when the potential is changed from the fully reduced to the fully oxidized state, independently of the dopant acid, The film obtained from the polymer doped with p-toluene-sulfonic acid, however, presents the highest contrast. Photoelectrochemical experiments also showed that this material yields photocurrent when irradiated with monochromatic light (330 nm), and that the sign of the photocurrent depends on its oxidation state.4154167110711

Electrochemical impedance spectroscopy studies for chemically prepared poly(o-methoxyaniline) doped with functionalized acids

Poly(o-methoxyaniline) was prepared by the chemical oxidation of the monomer with ammonium peroxydisulfate in the presence of the following acids: hydrochloric, p-toluenesulfonic, dodecylbenzenosulfonic and dodecylsulfuric. The polymers obtained are soluble in dimethylformamide and this enabled the preparation of films by casting. The electrochemical behavior of the polymers prepared by chemical synthesis is very similar to polyaniline prepared by electrochemical methods. Impedance spectroscopy measurements indicated that the acid affects mainly the potential range where the charge transfer resistance is lower. The diffusion coefficients obtained by impedance spectroscopy are higher for poly(o-methoxyaniline) doped with chloridric and p-toluene sulfonic acids than for those doped with dodecylbenzenosulfonic and dodecylsulfuric acids. (C) 1997 Elsevier Science Ltd.434179545746

Photoelectrochemical properties of poly (3,4-ethylenedioxythiophene)

The photoelectrochemical properties of poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonate) in contact with an electrolytic solution containing a redox couple were studied using the theories for the semiconductor-electrolyte interface. When this polymer-electrolyte interface is illuminated with h nu > Eg (gap energy) it exhibits cathodic photocurrent typical of p-type semiconductors, and the flat band potential, density of majority carriers, and the depletion layer thickness can be determined. To complete the band energy diagram of this polymer-electrolyte interface we obtained the band gap energy through the absorption and photocurrent spectra. The relatively low band gap energy (1.5 eV) and the photoeffects observed at the interface suggest its use as the absorbing material in photoelectrochemical cells.104266124612

Solid-state photoelectrochemical cell using a polythiophene derivative as photoactive electrode

In this work, we investigated the photoelectrochemical behavior of poly(4,4 ' -dipentoxy-2,2 ' -bithiophene), poly(ET2), as a single electrode in a liquid electrolyte and also its use in a solid-state photoelectrochemical device using a polymeric electrolyte. The results showed a strong dependence of the photocurrent density on the type and concentration of the redox couple. The solid-state device exhibited a short-circuit current density of 4 muA cm(-2) and an open-circuit voltage of 9 mV. The maximum quantum yield of photocurrent in the visible range was 0.17%, high when compared to other photoelectrochemical devices based on organic materials; however, it is low in comparison to solid-state devices using inorganic materials. This paper shows the viability of using organic polymeric electrolytes in the construction of photoelectrochemical devices, (C) 2001 Elsevier Science BN. All rights reserved.69431532

Polymer electrolytes based on ethylene oxide-epichlorohydrin copolymers

In this work we studied the ionic conductivity for three copolymers of the title co-monomers as a function of LIClO4 content, temperature and ambient relative humidity. We also investigated the interactions between the salt and the co-monomer blocks in the copolymers and its effect on the morphology and thermal properties of the copolymer/salt complexes. Our data indicate that the Li+ ion predominantly interacts with the ethylene oxide repeating units of the copolymers. The copolymer with the highest ionic conductivity was obtained with an ethylene oxide/epichlorohydrin ratio of 84/16 containing 5.5% (w/w) of LiClO4. It showed a conductivity of 4.1 X 10(-5) S cm(-1) (30 degrees C, humidity < 1 ppm) and 2.6 X 10(-4) S cm(-1) at 84% relative humidity (24 degrees C). The potential stability window of the copolymer/salt complex is 4.0 V, as measured by cyclic voltammetry. For comparison, we also prepared a blend of the corresponding homopolymers containing LiClO4; it showed higher crystallinity and lower ionic conductivity. (C) 2000 Elsevier Science B.V. All rights reserved.1304173228129

Influence of dopant, pH and potential on the spectral changes of poly(o-methoxyaniline): relationship with the redox processes

Poly(o-methoxyaniline) films doped with functionalized acids show high solubility in conventional organic solvents and a high optical contrast between the reduced and the oxidized forms. They are also more stable towards thermal treatment than when they are doped with HCl. These characteristics make them suitable for use in electrochromic displays. The electrochromic behavior of this soluble derivative of polyaniline was investigated in detail by comparing the curves obtained by the differentiation of absorbance at fixed wavelengths with simultaneously obtained voltammograms. This analysis allows the chromophore species producing color changes to be related to the redox processes taking place during the electrochemical cycling. Molar absorptivities were calculated and the effect of pH on the absorption spectra of the emeraldine form of the polymer is also reported. (C) 1997 Elsevier Science S.A.4404167119319

A new configuration of the solid-state battery: magnesium polymer proton conductor gold, based on the use of poly(o-methoxyaniline)

A solid-state battery was constructed by interfacing a pressed pellet of poly(o-methoxyaniline), in the emeraldine form with p-toluene sulfonic acid as doping agent, to a magnesium electrode covered with a film of magnesium perchlorate; the contact on the poly(o-methoxyaniline) was done by means of a gold electrode. The so-obtained cell, Mg I magnesium perchlorate I poly(o-methoxyaniline) I gold, was able to supply energy with a power depending on discharge current and on environmental humidity. Values of power up to 2.5 mW cm(-2) at discharge currents of about 2 mA cm(-2) were reached. (C) 1997 Elsevier Science S.A.901313

New functionalized 3-(alkyl)thiophene derivatives and spectroelectrochemical characterization of its polymers

Three novel 3-[omega-(p-methoxyphenoxy)alkyllthiophene monomers were synthesized and electrochemically polymerized on ITO electrodes by potentiodynamic or potentiostatic methods. Potentiostatic deposition provided films with better stabilities and had smaller quantities of soluble oligomers formed during polymerization. We also observed that derivatives with shorter alkyl chains in the substituted thiophene are difficult to polymerize by electrochemical methods. Spectroelectrochemical characterization of the polymer films obtained showed that their colors depend on the alkyl chain length in the substituted monomer. This demonstrates that the electrochromic behavior of these polymers can be tailored by means of the chemical synthesis of the monomers. The electrochromic properties presented by these new polymers motivate their future application in electrochromic devices. (C) 2004 Elsevier B.V. All rights reserved.1451434