Electrochemical synthesis and characterization of poly(pyrrole-co-tetrahydrofuran) conducting copolymer

The direct electrochemical copolymerization of pyrrole and tetrahydrofuran in various monomer ratios was carried out by potentiostatic methods in nitromethane solution. The copolymer has been characterized using FT-IR, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetrical analysis (TGA), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and elemental analysis. The results showed that the electrochemical oxidation of pyrrole and tetrahydrofuran comonomers generated true copolymers rather than blends of the two homopolymers. The copolymer showed a better flexibility than pure polypyrrole. The electrical conductivity of the copolymers increases with the amount of polypyrrole in the copolymer between the value of 1.69 S/cm and 0.71 S/cm.     

Synthesis, characterization and electrochromic properties of conducting copolymers of 2,3-bis-[(3-thienylcarbonyl)oxy]propyl 3-thiophene carboxylate with thiophene and pyrrole

2,3-bis-[(3-thienylcarbonyl)oxy]propyl 3-thiophene carboxylate (TOPT) was synthesized via the reaction of 3-thionylcarboxylic acid with glycerol, and electrochemically polymerized either with thiophene and pyrrole by using tetrabutylammonium tetrafluoroborate (TBAFB) as the supporting electrolyte in acetonitrile (AN). Characterization of the resulting copolymers was performed via cyclic voltammetry, FTIR, thermal gravimetry analysis (TGA), and scanning electron microscopy (SEM). Electrical conductivities were measured by the four-probe technique. Spectroelectrochemical analysis shows that the copolymer of the monomer with thiophene has an electronic band gap (due to the π-π^∗ transition) of 2.00 eV, with a dark red color in the fully reduced form and a green color in the fully oxidized form. The copolymer exhibited a long-term switching stability up to 1800 double switches.     

Electrosyntheses and characterization of polyalkylenedioxybenzenes

Direct anodic oxidation of 1,2-methylenedioxybenzene (MDOB) and 1,2-ethylenedioxybenzene (EDOB), analogues of 3,4-alkylenedioxythiophene and 3,4-alkylenedioxypyrrole, led to the formation of polyacetylene derivatives, poly(1,2-methylenedioxybenzene) (PMDOB) and poly(1,2-ethylenedioxybenzene) (PEDOB), on a platinum sheet in pure boron trifluoride diethyl etherate (BFEE). IR, ¹H NMR, ¹³C NMR and quantum chemistry calculations confirmed that the polymerization occurred at C(4) and C(5) position on the benzene ring of the monomer, making the main backbone of PMDOB and PEDOB similar to polyacetylene. Both dedoped PMDOB and PEDOB in DMSO solution showed good fluorescence properties with quantum yields of 0.13 and 0.27, emitting blue and green light under excitation of 365 nm, respectively. PMDOB showed electrochromic properties from grass green (doped) to light nacarat (dedoped). PEDOB changed it from bottle green (doped) to nacarat (dedoped). Doped PMDOB and PEDOB own electrical conductivities of 0.1 S cm⁻¹ and 0.17 S cm⁻¹, respectively.     

Synthesis and characterization of a new soluble conducting polymer and its electrochromic device

A mixture of isomers 2,5-di(4-methyl-thiophen-2-yl)-1-(4-nitrophenyl)-1H-pyrrole, 2-(4-methyl-thiophen-2-yl)-5-(3-methyl-thiophen-2-yl)-1-(4-nitrophenyl)-1H-pyrrole and 2,5-di(3-methyl-thiophen-2-yl)-1-(4-nitrophenyl)-1H-pyrrole (Me-SNS(NO₂)) were synthesized. Resulting monomers were polymerized chemically, producing soluble polymers in common organic solvents. The average molecular weight has been determined by gel permeation chromatography (GPC) as Mn=5.6×10³ for the chemically synthesized polymer. The monomers were also electrochemically polymerized in the presence of LiClO₄, NaClO₄ (1:1) as the supporting electrolyte in acetonitrile solvent. Resulting polymers were characterized via CV, FTIR, NMR, SEM and UV–Vis spectroscopy. Spectroelectrochemistry analysis of polymer revealed Π–Π^* transition below 300 nm, with an electronic band gap of 2.18 ev. Switching ability of the polymer was evaluated by kinetic study measuring percent transmittance (%T) at the maximum contrast point, indicating that poly(Me-SNS(NO₂)) is a suitable material for electrochromic devices.     

Synthesis and characterization of a bifunctional amido-thiophene monomer and its copolymer with thiophene and electrochemical properties

A bifunctional amido-thiophene namely hexamethylene (bis-3-thiophene acetamide) (HMTA) was synthesized by the reaction of 3-thiophene acetic acid with hexamethylene diamine. Copolymerization in the presence of thiophene was achieved electrochemically in tetrabutylammonium tetrafluoroborate/acetonitrile (TBAFB/AN). Spectroelectrochemical analysis of the resulting copolymer [P(HMTA-co-Th)] reflected electronic transitions at 505 nm, 740 nm and ∼1000 nm, revealing π to π* transition, polaron and bipolaron band formation respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual type polymer electrochromic devices (ECDs) based on P(HMTA-co-Th) and poly(ethylene dioxythiophene) (PEDOT) have been constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-vis spectroscopy and cyclic voltammetry. These devices exhibit low switching voltages (between 0.0 V and +1.6 V), short switching times with reasonable switching stability under atmospheric conditions.     

Synthesis and characterization of degradable electrically conducting copolymer of aniline pentamer and polyglycolide

A novel block copolymer of polyglycolide (PGA) and aniline pentamer that is electro-active and degradable was synthesized. The copolymer was prepared by low-temperature polycondensation between carboxyl-capped aniline pentamer and hydroxyl-capped PGA, with N,N′-dicyclohexylcarbodiimide (DCC) as dehydrating agent. The structures of monomers and the copolymer were characterized by IR, ¹H NMR. The chemical redox process of the as-prepared copolymer was studied by UV-vis spectra and cyclic voltammetry (CV). Thermal analysis and the study of degradation show that the copolymer has good thermal stability and degradability.     

Low-potential electrosynthesis of conducting and electroactive oligocatecholborane with blue light-emitting properties

Novel conducting oligocatecholborane (OCOB) with electrical conductivity of 3.73 × 10-2S cm-1 was successfully synthesized by low-potential electropolymerization of catecholborane (COB) in boron trifluoride diethyl etherate at 0.70 V versus Ag/AgCl. FT-IR and 1H-NMR spectra, together with the computational results, proved that COB was polymerized through the coupling at C(4) and C(5) positions and the reactive B―H bond was stable during the electrochemical polymerization. The resulting product was mainly composed of oligomers with short chain lengths by GPC and mass spectral results. The as-formed OCOB film showed good electrochemistry in monomer-free electrolytes with the electrochromic property from opaque blue to sap green. Fluorescence studies indicated that soluble OCOB can emit bright blue light under excitation of 365 nm UV light with the maximum emission at 396 nm and a fluorescence quantum yield of 0.21. The deposited OCOB also exhibited favorable thermal stability and smooth and compact morphology even at high magnifications.     

Electrosyntheses and characterization of poly(9-bromophenanthrene) in boron trifluoride diethyl etherate

A novel semi-conducting polymer poly(9-bromophenanthrene) (P9BP) was synthesized electrochemically by direct anodic oxidation of it is monomer 9-bromophenanthrene (9BP) in boron trifluoride diethyl etherate (BFEE). The oxidation onset potential of 9BP in this medium was measured to be only 1.33 V vs. saturated calomel electrode (SCE). P9BP films obtained from BFEE showed good electrochemical behavior and nice thermal stability with electrical conductivity of 0.03 S cm⁻¹. FTIR and ¹H NMR spectra together with theoretical quantum chemistry calculations indicated that the P9BP was mainly grown via the coupling of the monomer at C₃ and C₆ positions. Furthermore, P9BP exhibited strong electrochromic nature from opaque green to light yellow between the doped and dedoped states on ITO electrode in solid state. Fluorescence spectral studies indicated that P9BP was a blue light emitter.     

Electrochemical preparation of a soluble conducting aniline-thiophene copolymer

A new of soluble sulfonated conductive copolymer has been synthesized by electrochemical oxidation in the presence of anhydrous FSO₃H. The sulphur-to-nitrogen ratios indicated that copolymers were formed in addition to the incorporation of groups into polymeric backbone. The sulfonated copolymer films have better solubility in DMSO and KOH. The conductivity of the copolymer films increases with the increase in the number of thiophene rings in the polymeric backbone. Copolymer films synthesized were investigated by cyclic voltammetry, UV-visible, FT-IR and ¹H-NMR spectroscopy, dry conductivity and intrinsic viscosity measurements, elemental analysis and SEM pictures.     

Molecularly imprinted conducting polymer based electrochemical sensor for detection of atrazine

An original electrochemical sensor based on molecularly imprinted conducting polymer (MICP) is developed, which enables the recognition of a small pesticide target molecule, atrazine. The conjugated MICP, poly(3,4-ethylenedioxythiophene-co-thiophene-acetic acid), has been electrochemically synthesized onto a platinum electrode following two steps: (i) polymerization of comonomers in the presence of atrazine, already associated to the acetic acid substituent through hydrogen bonding, and (ii) removal of atrazine from the resulting polymer, which leaves the acetic acid substituents open for association with atrazine. The obtained sensing MICP is highly specific towards newly added atrazine and the recognition can be quantitatively analyzed by the variation of the cyclic voltammogram of MICP. The developed sensor shows remarkable properties: selectivity towards triazinic family, large range of detection (10⁻⁹ mol L⁻¹ to 1.5 × 10⁻² mol L⁻¹ in atrazine) and low detection threshold (10⁻⁷ mol L⁻¹).     

A new self-doped copolymer consisting of 3-methyl thiophene and aniline units

The copolymer films of sulfonated aniline and sulfonated 3-methyl thiophene were synthesized by electrochemical polymerization. The sulfonated copolymer films have better solubility in DMSO and KOH than the corresponding homopolymers. The conductivity of the copolymer films increase with the increase in the number of thiophene rings in the polymeric backbone. Copolymer films synthesized were investigated by cyclic voltammetry, UV-visible and FT-IR spectroscopy, dry conductivity and intrinsic viscosity measurements and elemental analysis. The elemental analysis and UV-visible spectroscopic results show that copolymer films have properties intermediate between the two homopolymers.     

聚3-(4-氟苯基)噻吩/碳化聚丙烯腈泡沫复合电极的电化学研究

噻吩衍生物是合成导电高分子材料的单体之一,在有机电致发光器件和电能存储等方面有着广泛的应用。聚3-(4-氟苯基)噻吩(PFPT)是一类既可进行p型掺杂又可进行n型掺杂的窄能带聚合物,在导电高分子型电化学电容器方面具有很好的应用前景,聚丙烯腈微孔膜已在锂离子电池方面有了很好的应用。若将它与碳纸复合后,再进行高温碳化和CO2活化,可制得导电性好、比表面积大的片状材料,作为电化学电容器的电极材料具有一定的双电层电容量．本文在三电极电解池中以这种材料的薄片为工作电极使3-(4-氟苯基)噻吩在乙腈溶液中进行电化学聚合,制备了聚3-(4-氟苯基)噻吩／碳化聚丙烯腈泡沫复合电极并研究了电极的电化学特性。     

Novel thiophene based colorimetric and fluorescent receptor for selective recognition of fluoride ions

A colorimetric anion sensor 2,2′-(1E,1′E)-(thiophene-2,5-diylbis(methan-1-yl-1-ylidene)) was synthesized and characterized by various spectroscopic techniques. Anion binding studies were carried out using UV-visible spectrophotometric titrations and emission spectra studies, revealed that the receptor exhibits selective recognition toward F⁻over other anions. The selectivity for F⁻among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F⁻. Receptor 1 showed color change from fluorescent green to orange in the presence of tetrabutylammonium fluoride with 1:1 stoichiometry. Receptor 1 exhibits remarkably enhanced fluorescence intensity.     

An extended tetrathiafulvalene redox-ligand incorporating a thiophene spacer

An extended tetrathiafulvalene derivative incorporating a thiophene spacer and a fused crown-ether unit has been synthesized. This highly delocalized system exhibits remarkable electrochemical recognition properties for Na⁺ and Ba²⁺ as shown by cyclic voltammetry in methylene chloride. This result is attributed to the proximity between the guest metal cation and the positive charge of the oxidized ligand, which is located on the central conjugated thiophenic part.     

Polyaniline coated conducting fabrics. Chemical and electrochemical characterization

Polyaniline coated conducting fabrics have been obtained by chemical oxidation of aniline by potassium peroxydisulfate on polyester fabrics. Two different acids have been employed to carry out the synthesis (HCl and H₂SO₄), obtaining the best results of conductivity with the latter one. The conducting fabrics have been characterized chemically by means of Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), energy dispersive X-Ray (EDX) and X-ray photoelectron spectroscopy (XPS). The morphology of the coatings has been observed by means of scanning electron microscopy (SEM). The conducting properties of the fabrics have been measured by means of electrochemical impedance spectroscopy (EIS). The electrochemical characterization has been carried out by means of cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The conducting fabrics have also shown electrochromic properties, changing its color from green yellowish at −1 V to dark green at +2 V. The durability of the coating has been evaluated by means of washing and rubbing fastness tests.     

Detection of deletion mutations in DNA using water-soluble cationic fluorescent thiophene copolymer

In this contribution, we designed a fluorescent thiophene copolymer to detect insertion/deletion mutation in DNA by doping aldehyde group in the main chain. The fluorescence of the copolymer could be dramatically quenched on the addition of single-stranded DNA (ssDNA) via strong electrostatic interactions and electronic/energy transfer. Although the complementary ssDNA made the fluorescence recover, the hydrogen bonds and chemical coupling also played a significant role between the unpaired bases and aldehyde group, which could differentiate the subtle differences in such mutant DNA. The influence of buffer pH, concentration of NaCl, heating time and the temperature was systemically investigated and the proposed method was then successfully applied to detect real sample. With the respect to the linearity, limit of detection precision, specificity, this procedure could provide sensitive methodologies for the rapid detection and identification of nucleic acids.     

Electrosynthesis of highly conducting poly(1,5-dihydroxynaphthalene) in BF3·Et2O

Direct anodic oxidation of 1,5-dihydroxynaphthalene (DHN), an important derivative of naphthalene, led to the formation of high-quality semiconducting poly(1,5-dihydroxynaphthalene) (PDHN) on stainless steel sheets in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of DHN in this medium was measured to be only 0.78 V vs. SCE, which was lower than that determined in traditional acetonitrile containing 0.1 mol/L tetrabutylammonium tetrafluoroborate (0.98 V vs. SCE). As-formed PDHN films showed good redox activity and stability, together with interesting electrochromic property from brown (doped) to yellow-green (dedoped). Structural characterization, including FTIR, ¹H NMR, and quantum chemistry calculations, indicated that the polymerization of DHN probably occurred at C₄ and C₈ positions. Moreover, thermal analysis revealed that PDHN displayed better thermal stability than that synthesized by chemical method. The fluorescence spectral studies, together with the electrical tests, showed that PDHN was a good blue light-emitter (fluorescence quantum yield higher than 0.1) with an electrical conductivity of as high as 0.46 S/cm.     

New conducting pyrrole–thiophene co-polymer from an oligomer precursor: electrochemical characterisation

A new oligomer of N,N′-bis(2-pyrrolyl methylene)-3,4-dicyano-2,5-diaminothiophene possessing cyano-substituted 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 (TBABF₄)/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 TBABF₄, tetrabutylammonium perchlorate (TBAClO₄), lithium perchlorate (LiClO₄) and sodium perchlorate (NaClO₄) 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.     

Electrosyntheses of high quality poly(5-methylindole) films in mixed electrolytes of boron trifluoride diethyl etherate and diethyl ether

High quality poly(5-methylindole) (P5MeI) films, especially with good fluorescence properties, were synthesized electrochemically by direct anodic oxidation of 5-methylindole in boron trifluoride diethyl etherate (BFEE) containing additional 50% diethyl ether (EE) (by volume). The oxidation potential onset of 5-methylindole in this medium was measured to be only 0.84 V vs. SCE, which was much lower than that determined in acetonitrile + 0.1 mol L⁻¹ TBATFB (1.08 V vs. SCE). P5MeI films obtained from this medium showed good electrochemical behavior and good thermal stability with conductivity of 10⁻² S cm⁻¹, indicating that BFEE was a better medium than acetonitrile for the electrosyntheses of P5MeI films. Dedoped P5MeI films were thoroughly soluble in strong polar solvent such as dimethyl sulfoxide (DMSO). ¹H NMR spectroscopy and FT infrared spectrum of dedoped P5MeI films strongly suggested that the monomers were linked via the positions 2 and 3. Fluorescent spectral studies indicated that P5MeI was a good violet-blue light emitter with the excitation and emission wavelength of 310 nm and 418 nm, respectively. To the best of our knowledge, this is the first case that 5-methyl group substituted polyindole films with good fluorescence properties can be electrodeposited.