Low potential electrodeposition of high‐quality and freestanding poly(3‐(6‐bromohexyl)thiophene) films

High‐quality freestanding and conducting poly[3‐(6‐bromohexyl)thiophene] (PBHT) films with electrical conductivity of 20 S/cm were synthesized electrochemically by direct anodic oxidation of 3‐(6‐bromohexyl)thiophene (BHT) in boron trifluoride diethyl etherate (BFEE). The oxidation potential of BHT in pure BFEE was measured to be only 1.2 V versus saturated calomel electrode, SCE much lower than that determined in acetonitrile (ACN) (1.8 V vs SCE). The polymer films obtained from this media were very shiny and flexible and can be easily cut into various shapes. The structure and morphology of the polymer films were investigated by UV‐vis, infrared, ¹H‐NMR spectroscopy, thermal analysis, and scanning electron microscopy (SEM). All these results indicated that the terminal bromide did not have negative effect on the electrochemical polymerization of BHT. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrochemical polymerization of 2‐phenylindole and characterization of its polymer

High‐quality poly(2‐phenylindole) (PPI) films were synthesized electrochemically by direct anodic oxidation of 2‐phenylindole (PI) in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of PI in this medium was measured to be only 0.83 V versus a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile (ACN) containing 0.1 mol L^–1 tetrabutylammonium tetrafluoroborate (1.05 V vs. SCE). PPI films obtained from BFEE showed good electrochemical behavior and thermal stability with an electrical conductivity of 10^–2 S cm^–1. Structural studies showed that the polymerization of PI mainly occurred at the 3,6‐positions. As‐formed PPI films could be partly dissolved in dimethyl sulfoxide. Fluorescence spectral studies indicated that PPI was a blue‐green light emitter. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrosyntheses of high quality free-standing poly(9-fluorenone) films in boron trifluoride diethyl etherate

High quality free-standing poly(9-fluorenone) (PFO) films were synthesized electrochemically by direct anodic oxidation of 9-fluorenone (FO) in pure boron trifluoride diethyl etherate (BFEE). The oxidation potential of FO in this medium was measured to be only 1.48 V versus SCE, which was greatly lower than that determined in CH₂Cl₂ + 0.1 mol l⁻¹ Bu₄NBF₄ (2.21 V versus SCE). PFO films obtained from BFEE showed good electrochemical behavior, good thermal stability with electrical conductivity of 7.8 × 10⁻³ S cm⁻¹, indicating that BFEE was a better medium than CH₂Cl₂ for the electrosyntheses of PFO films. Structural studies showed that the polymerization of FO ring occurred at 2,7-position. As-formed PFO films can be partly dissolved in acetone and tetrahydrofuran (THF). Fluorescent spectral studies indicate that PFO is a good blue light emitter. To the best of our knowledge, this is the first report on the electrosyntheses of free-standing PFO films.     

Electrodeposition of High-quality Polycarbazole Films in Composite Electrolytes of Boron Trifluoride Diethyl Etherate and Ethyl Ether

High-quality polycarbazole (PCZ) films were synthesized electrochemically by direct oxidation of carbazole in boron trifluoride diethyl etherate (BFEE) containing vol. 20% ethyl ether (EE). The oxidation potential of carbazole in this medium was measured to be only 0.90 V vs. SCE, which was lower than that determined in acetonitrile containing 0.1 mol l⁻¹ Bu₄NBF₄ (1.35 V vs. SCE). PCZ films obtained from this medium showed better electrochemical behavior, better thermal stability with conductivity of 7.5 × 10⁻³ S cm⁻¹ being one order of magnitude higher than those reported previously, indicating that BFEE/EE was a better medium than acetonitrile for the electrosyntheses of PCZ films. As-formed PCZ films can be partly dissolved in acetone, acetonitrile and tetrahydrofuran. Spectral analysis provided evidence for the existence of the conjugated structure of the PCZ chain. Fluorescent spectra indicate that electrosynthesized PCZ is an ideal blue light emitter.     

Electrosynthesis of free‐standing poly(para‐phenylene) films in mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid on stainless steel electrode

Free‐standing poly(para‐phenylene) (PPP) films have been electrosynthesized by direct oxidation of benzene on stainless steel electrode in mixed e1ectrolytes of boron trifluoride diethy1 etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potential of the monomer in these media is lower than those in the neutral media. Increasing the content of TFA in the mixed electrolyte can effective1y decrease the oxidation potential and increase the coup1ing rate of the monomer. The films obtained from these media were very shiny and flexible, and could easily be processed into various shapes by conventional mechanical methods. The films had a 1inear chain structure, and their degree of polymerization could be improved by increasing the TFA content in the mixed electrolyte. Moreover, the films had a fairly good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2462–2466, 2002     

Facile electrosynthesis of nitro-group-substituted oligopyrene with bicolored emission

Nitro-group-substituted oligopyrene (ONP) film with fairly high electrical conductivity (1.25 × 10⁻¹ S cm⁻¹) and good thermal stability was electrochemically synthesized by direct anodic oxidation of its monomer 1-nitropyrene (NP) in boron trifluoride diethyl etherate (BFEE). The oxidation potential of NP in this medium was determined to be 1.12 V vs. SCE, which was lower than that in acetonitrile +0.1 mol L⁻¹ Bu₄NBF₄ (1.27 V vs. SCE). ONP films obtained from this medium showed good redox activity and structural stability in both BFEE and concentrated sulfuric acid. Fourier transform infrared spectra and theoretical calculations showed that the electropolymerization of the NP monomer mainly occurred at the C(3), C(6) and C(8) positions. The fluorescence spectra suggested that soluble ONP emits strong blue or green fluorescence when excited at 402 nm or 504 nm, respectively. Scanning electron microscopy showed that highly crystalline nitro-group-substituted oligopyrene was formed on the electrode surface. All these results indicate that as-prepared ONP film has many potential applications in various fields.     

Electrochemical polymerization of β‐naphthalene sulfonic acid

β‐Naphthalene sulfonic acid (β‐NSA) has been electrochemically polymerized in a mixed electrolyte of boron trifluoride diethyl etherate (BFEE) solution mixed with a certain amount of trifluoroacetic acid (TFA) or concentrated sulfuric acid (SA). The poly(β‐naphthalene sulfonic acid) (PNSA) film prepared from the medium of BFEE+TFA was partly soluble in methanol. On the other hand, the polymer obtained from the system of BFEE+SA was soluble in water and general polar organic solvents such as methanol, alcohol, and acetone. The structure of PNSA was examined by infrared and UV spectra. Fluorescent spectral studies indicate that the polymer is a blue light emitter with fluorescence quantum efficiency of ～ 4%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1939–1944, 2004     

Electrochemical polymerization of p‐terphenyl in mixed electrolyte of boron trifluoride diethyl etherate and CH2Cl2

High quality poly(p‐phenylene) (PPP) film with conductivity of 0.015 S cm^?1 was synthesized electrochemically by direct anodic oxidation of p‐terphenyl (PP) oligomers in boron trifluoride diethyl etherate (BFEE) containing 37.5% CH₂Cl₂ (v/v). The oxidation onset potential of PP in this medium was measured to be only 1.23 V vs. saturated calomel electrode (SCE), which was lower than that determined in CH₂Cl₂ + 0.1 mol L^?1 Bu₄NBF₄ (1.87 V vs. SCE). As‐formed PPP films showed good electrochemical behavior, good electrochromic property and good thermal stability. The structures and morphology of doped and dedoped PPP were investigated by UV‐vis, FTIR, and Scanning electron micrographs. The infrared spectroscopic measurements for the estimation of chain lengths revealed that PPP was composed of about 10 phenyl rings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Tricolor electrochromism of PEDOT film electrodeposited in mixed solution of boron trifluoride diethyl etherate and tetrahydrofuran: Hypsochromic effect

PEDOT [poly (3,4‐ethyldioxythiophene)] films have been electrochemically prepared in mixed solution of boron trifluoride diethyl etherate and tetrahydrofuran (BFEE‐THF). The film shows tricolor electrochromism which is claret red at ?0.8 V, light grey at 0.2 V, and sea blue at 1.0 V. The film retains 74% of the original electroactivity and unperturbed electrochromic behaviors after 3000 cycles indicating potential applications on EC devices. Spectroelectrochemistry indicates that the π‐π* transition absorption peak (λ_max) in the neutral state is located at 512 nm and the calculated energy gap (E_g) is 1.76 eV by the onset wavelength. Compared to the electropolymerization of PEDOT films in conventional solvent, tricolor electrochromism can be ascribed both to the low onset oxidation potential and polymerization rate in BFEE‐THF, which may result in a low conjugation length of PEDOT. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Low‐potential electrochemical polymerization of 6‐nitroindole and characterization of its polymers

Conducting polymers bearing nitro substituents are very important from both academic and industrial viewpoints. However, it is very difficult to electrosynthesize such conducting polymers because of the strong electron‐withdrawing effect of nitro groups. In this article, we describe the electrochemical synthesis of films of a new conducting polymer, high‐quality poly(6‐nitroindole) (P6NI), by direct anodic oxidation of 6‐nitroindole in boron trifluoride diethyl etherate containing 10% (v/v) diethyl ether. The oxidation potential onset of 6‐nitroindole in this medium has been measured to be just 0.98 V versus a saturated calomel electrode (SCE), which is much lower than that determined in acetonitrile containing 0.1 mol/L tetrabutylammonium tetrafluoroborate (1.6 V vs SCE). Thermal studies have revealed that P6NI displays good thermal stability. The electrical conductivity of the P6NI films has been measured to be 0.08 S/cm. Structural studies have shown that the polymerization of the 6‐nitroindole ring occurs mainly at the 2,3‐positions. Fluorescence spectral studies have shown that the principal excitation and emission peaks of P6NI are at 416 and 535 nm, respectively, with a fluorescence quantum yield of 0.05. All these properties of P6NI films may facilitate their potential applications in various fields, such as electrochemical sensors and green‐light‐emitting materials. To the best of our knowledge, this is the first report on the electrosynthesis and characterization of 6‐nitro‐substituted polyindole films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Impedance study of the passive film on stainless steel 304 in pH 8 carbonate solution

The effects of applied d.c. potential and polarization time on the passivation of stainless steel 304 (SS304) were investigated in deaerated 1 M NaHCo₃ aqueous solutions at pH 8. Electrochemical impedance spectroscopy was used in conjunction with a rotating disc electrode. The data were analysed by considering an equivalent circuit. The changes in impedance parameters at applied d.c. potential signal changes in the properties of passive films on SS304 and allow to distinguish the parameters at low potential (–0.6 to 0.3 V vs SCE) from a different one at high potential (0.5 to 0.8 V vs SCE). The oxidation reactions were controlled by both charge transfer and mass transfer processes. Diffusional resistance was high for both passive films and was considered to represent the resistance to movement of ions or vacancies through the surface layer of oxide films. It is deduced that the passive film present in the low potential region is partially dissolved at 0.4 V vs SCE and that a new passive film is formed in the higher potential region. The equivalent circuit used to obtain the best fit and the fitting parameters was dependent on the electrode potential and the polarization time. The reproducibility of the impedance spectra at constant potentials demonstrate that the passive film formation is highly irreversible process. No traces of localized corrosion were detected but, for a high potential and long polarization time, the electrode surface coloration to a uniform gold colour confirms the film thickening.     

Anodic, cathodic and cyclic voltammetric deposition of ruthenium oxides from aqueous RuCl3 solutions

Anodic, cathodic and cyclic voltammetric (CV) deposition of ruthenium oxides from aqueous RuCl₃ solutions have been investigated using stationary and rotating disk electrodes (RDE) in this work. The CV deposition behavior was examined using a RDE to differentiate the contribution of current from the reactions of ruthenium ions in the electrolyte and ruthenium oxides already adsorbed on the electrode. The results indicate that the CV growth of ruthenium oxides within the potential range of aqueous electrolyte decomposition is attributed to the anodic oxidation of ruthenium ions in the electrolyte. Cathodic deposition occurs only at potential negative than −0.30 V versus saturated calomel electrode (SCE) when H₂ evolves on the electrodes. Anodic deposition of ruthenium oxides can be obtained effectively in the potential range of ca. 0.9-1.1 V versus SCE, depending on the pH value of the electrolyte. The optimum anodic and cathodic deposition potential for maximum deposition efficiency is 1.0 and −0.9 V versus SCE, respectively, in the electrolyte solution of pH 2.     

Electrochemical behavior of amorphous carbon obtained from camphor

Amorphous carbon films were deposited on alumina plate by pyrolysing camphor at different temperatures with thermal chemical vapor deposition (CVD) technique. Carbon coated alumina plates were used as working electrode to ascertain their electrochemical behavior in different electrolytic media. Electrochemical windows of these carbon films were found to be suitable in the potential range of 1.05 to −0.30 V versus SCE in acid medium. In the presence of redox electrolyte, cathodic-anodic peak separation was found to be the same as that obtained with diamond. Raman spectra of carbon films were studied to explain some of their electrochemical behavior.     

Direct low‐potential electropolymerization of 9,10‐dihydrophenanthrene in boron trifluoride diethyl etherate

High‐quality poly(9,10‐dihydrophenanthrene) (PPh) with good fluorescence properties was synthesized electrochemically by the direct anodic oxidation of 9,10‐dihydrophenanthrene in boron trifluoride diethyl etherate (BFEE). PPh films obtained from BFEE‐based electrolytes showed good electrochemical behavior and good thermal stability with an electrical conductivity of 2.2 × 10^?3 S/cm; this indicated that BFEE was a better medium for the electrosyntheses of PPh films. Dedoped PPh films were soluble in CH₂Cl₂, dimethylformamide, and dimethyl sulfoxide. The structure and morphology of the polymer were also characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and scanning electron microscopy, respectively, which indicated the polymerization mainly occurred at the C₍₂₎ and C₍₇₎ positions. Fluorescent spectral studies indicated that PPh was a good blue‐light emitter. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrochemical deposition of polyaniline–polypyrrole composite coatings on aluminum

The electrodeposition of polyaniline–polypyrrole composite coatings on aluminum was successfully performed by using cyclic voltammetry. Oxalic acid was used as the electrolyte. Electrodeposition was carried out at a scan rate of 20 mV/s by varying the number of cycles. An anodic peak current at around ?0.1 V versus saturated calomel electrode (SCE) was observed in the cyclic voltammograms. This peak is due to the oxidation and adsorption of hydrogen. The cyclic voltammograms also show another anodic peak current at around 1.0 V versus SCE, which is the characteristic peak of the polyaniline–polypyrrole composite. The behavior of this peak with respect to the number of cycles is discussed in detail. A corresponding cathodic peak current at around ?0.7 V versus SCE was also observed in the cyclic voltammograms. The infrared spectra of the composite coatings revealed the infrared peaks of both polypyrrole and polyaniline. The scanning electron micrographs of the coatings indicate a morphology completely different from its homopolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1970–1977, 2002     

Electrochemical polymerization of phenanthrene in mixed electrolytes of boron trifluoride diethyl etherate and concentrated sulfuric acid

A novel high‐quality polyphenanthrene (PPH) film with electrical conductivity of 10^?1 S cm^?1 was synthesized electrochemically by direct anodic oxidation of phenanthrene in boron trifluoride diethyl etherate containing 10% concentrated sulfuric acid (v/v). The oxidation onset potential of phenanthrene in this medium was measured to be only 0.91 V versus saturated calomel electrode (SCE), which was lower than that determined in acetonitrile + 0.1 mol L^?1 Bu₄NBF₄ (1.56 V versus SCE). As‐formed PPH films from this medium showed good electrochemical behavior and stability. De‐doped PPH films were thoroughly soluble in dimethylsulfoxide or CHCl₃. The structure and morphology of the polymer were investigated using UV‐visible and Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy. FTIR and ¹H NMR spectra showed that the PPH was grown via the coupling of the monomer mainly at the C₄, C₅, C₉ and C₁₀ positions. Fluorescence spectral studies indicated that PPH was a blue‐green light emitter. Copyright © 2007 Society of Chemical Industry     

Electrochemical preparation of polythiophene in acetonitrile solution with boron fluoride–ethyl ether as the electrolyte

Polythiophene (PTh) films were prepared by the electrochemical polymerization of thiophene in acetonitrile solution with boron fluoride–ethyl ether (BFEE) as the electrolyte. The electropolymerization processes were investigated by cyclic voltammetry. The onset potential of the electropolymerization decreased dramatically with increasing BFEE proportion in the solution. The free‐standing PTh films obtained were characterized by Founier transform infrared spectroscopy, scanning electron microscopy, and X‐ray photoelectron microscopy. The influence of BFEE on the morphology and conductivity of the PTh films was also examined. The binary solvent solution consisted of acetonitrile (10 vol %) and BFEE (90 vol %), which turned out to be the optimal electrosythesis system, in which a current density of 1 mA/cm² and a monomer concentration of 50 mM were the optimal conditions for electropolymerization. The PTh film obtained under the optimized conditions had a high tensile strength of 60 MPa and a high conductivity of 153 S/cm. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 940–946, 2003     

Electrochemical synthesis and redox behaviour of polypyrrole coatings on copper in salicylate aqueous solution

In this work, polypyrrole (PPy) coatings have been successfully electrodeposited on copper substrates from aqueous salicylate solutions. Homogenous and uniform films can be grown under galvanostatic or potentiostatic control without noticeable substrate dissolution. The redox behaviour obtained for the films is similar to that displayed by PPy grown under the same conditions on noble metals. Strong adherence to copper is observed as far as PPy is in its oxidised state but it is lost when the system is subjected to potentials lower than −0.5 V versus saturated calomel electrode (SCE).     

基于原位红外光谱的水相苯酚电氧化机理研究

采用电化学原位红外光谱技术,研究了苯酚在Pt电极表面的电化学氧化机理。在0.1 mol/L Na₂SO₄溶液中,Pt电极上电化学氧化苯酚的反应电位为+0.9~1.0 V（vs SCE）、析氧电位为+1.3 V;电化学原位红外光谱结果表明,当电位<0.9 V时,苯酚氧化产物主要为苯二酚、醌及少量醇类物质;电位0.9~1.1 V时,苯环结构被破坏,氧化产物主要为酮、酸、醇和CO₂;根据官能团吸收峰的变化,苯酚在Pt电极表面氧化经历如下途径：苯酚→苯二酚→苯醌→酮、醇、酸→CO₂。同时研究了NH₄⁺对苯酚在Pt电极表面的电氧化的影响,结果表明在低电位区（<0.9 V）对苯酚氧化构成竞争。     

Behaviour of Al–Ga alloy during cathodic polarization

The effect of the addition of small quantities of gallium to high-purity aluminium (99.999 wt%) on its electrochemical behaviour at high cathodic potentials (up to −2.0 V versus SCE), has been investigated using the potentiostatic pulse method. After cathodic polarization, anodic current was traced versus time to determine the quantity of charge necessary for oxidation of substances formed. Anodic current responses to the return to the E _OCP were also recorded in the period of 1 s. Time responses of the cathodic and anodic currents were analyzed. The cyclic voltammetry method was used to determine the hydration potential. The range of low and high cathodic potentials (LCP, HCP) was defined for all the samples. It has been established that the oxide film retains its properties in the LCP range, while in the HCP range cathodic breakdown and hydration of the oxide take place. Electrochemical methods complemented the SEM and EDAX analysis before and after the cathode pulse of −1.9 V versus SCE.