Preparation, characterisation and biosensor application of conducting polymers based on ferrocene substituted thiophene and terthiophene

Novel ferrocene-substituted thiophene and terthiophene compounds, trans-1-(3′-thienyl)-2-(ferrocenyl)ethene and trans-1-((2′,2″:5″,2?-terthiophen)-3″-yl)-2-(ferrocenyl)ethene, have been used to produce homopolymer and copolymer materials. The copolymer of trans-1-(3′-thienyl)-2-(ferrocenyl)ethene with pyrrole and the homopolymer of trans-1-((2′,2″:5″,2?-terthiophen)-3″-yl)-2-(ferrocenyl)ethene were characterised using cyclic voltammetry (CV), UV-visible spectroscopy, scanning electron microscopy (SEM) and four point probe conductivity measurements. Results obtained suggest that the ferrocene moiety plays a catalytic role in the electropolymerisation process. Both the copolymer and homopolymer displayed cyclic voltammograms with redox peaks that can be assigned to the ferrocene moiety and the polymer backbone. The UV-visible spectra and morphology of the copolymer of trans-1-(3′-thienyl)-2-(ferrocenyl)ethene with pyrrole were similar to those of polypyrrole, but the spectra and morphology of the homopolymer of trans-1-((2′,2″:5″,2?-terthiophen)-3″-yl)-2-(ferrocenyl)ethene were different from those of polyterthiophene. The conductivity of the copolymer was determined to be 0.13 S cm⁻¹ whereas that of the homopolymer of trans-1-((2′,2″:5″,2?-terthiophen)-3″-yl)-2-(ferrocenyl)ethene was 82.6 μS cm⁻¹. The copolymer or homopolymer modified Pt disk electrodes facilitated access to the redox centre within Cytochrome C during CV, and their potential use as biosensors has been demonstrated.     

Reagentless recycling of pyruvate oxidase on a conducting polymer-modified electrode

The enzyme pyruvate oxidase (PyOD) covalently immobilized on an original conducting copolymer poly(5-hydroxy-1,4-naphthoquinone-co-5-hydroxy-3-thioacetic-1,4-naphthoquinone acid) can be recycled under anaerobic conditions, at +0.1 V versus SCE. It is first demonstrated that the quinone group is an efficient co-substrate for PyOD in homogeneous conditions, then this efficiency is preserved when the quinone group is embedded in the polymer structure. The copolymer remains efficient even in aerated media. The low working potential avoids side-oxidations of interfering species as ascorbic acid or salycilate.     

Studies of a novel conducting polymer by cyclic and square wave voltammetries: Its synthesis and characterization

A novel conducting polymer of polynaphthidine, poly(NAP), was synthesized electrochemically by direct anodic oxidation of naphthidine in aqueous media. The yield of the electropolymerization reaction depends on the temperature and pH of the solution. It was possible to differentiate two working regions: I (for pH < 0.5 and all temperatures) where the film yield tends to zero and II (for approximately 2.0 < pH < 2.8 and temperatures >15 °C) where the film production is maximum. Therefore, the naphthidine electrooxidation mechanism was studied under experimental conditions of region I by cyclic (CV) and square wave voltammetries (SWV) as well as by controlled potential electrolysis.The experimental conditions of region II were chosen to obtain the poly(NAP). The electrochemical response of the film was investigated in pH 1 HClO₄ + 0.1 M NaClO₄ electrolyte solution by CV and SWV. A plot of I_p,n/fvs. f from SW voltammograms showed the so-called “quasi-reversible maximum”. Formal potential, formal rate constant and anodic transfer coefficient for the surface redox process were also evaluated from the SWV.The poly(NAP) is insoluble in common organic solvents and shows electrochromic behaviour. Its probable structure was determined by FTIR spectroscopy.     

Proton conducting crosslinked polymer electrolyte membranes based on SBS block copolymer

A series of crosslinked polymer electrolyte membranes with controlled structures were prepared based on poly(styrene‐b‐butadiene‐b‐styrene) (SBS) triblock copolymer and a sulfonated monomer, 2‐sulfoethyl methacrylate (SEMA). SBS membranes were thermally crosslinked with SEMA in the presence of a thermal‐initiator, 4,4′‐azobis(4‐cyanovaleric acid) (ACVA), as confirmed by FT‐IR spectroscopy. The water uptake and ion exchange capacity (IEC) of membranes increased almost linearly with SEMA concentrations due to the increase of SO groups. However, the proton conductivity of membranes increased linearly up to 33 wt % of SEMA, above which it abruptly jumped to 0.04 S/cm presumably due to the formation of well‐developed proton channels. Microphase‐separated morphology and amorphous structures of crosslinked SBS/SEMA membranes were observed using wide angle X‐ray scattering (WAXS), small angle X‐ray scattering (SAXS), and transmission electron microscopy (TEM). The membranes exhibited good mechanical properties and high thermal stability up to 250°C, as determined by a universal testing machine (UTM) and thermal gravimetric analysis (TGA), respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Voltammetric sensor array based on conducting polymer-modified electrodes for the discrimination of liquids

In this work, a novel type of voltammetric electrodes based on conducting polymers has been developed and used as sensing units of a sensory system. Polymeric sensors have been obtained by electrodeposition of the corresponding monomers (3-methylthiophene, aniline and pyrrole) onto platinum disks using a range of doping agents. The electrochemical response of polypyrrole electrodes is particularly rich and stable. Moreover, their electrochemical characteristics can be improved by using large anions or redox anions as dopants.A multichannel liquid sensor has been constructed using those sensors showing the best performances in terms of stability and variety of responses. The array of sensors has been exposed to solutions with distinct taste properties (sweet, bitter, acid, salty and astringent). Each sensor shows a characteristic electrochemical response when exposed to the studied solutions, providing a high degree of cross-selectivity. The principal component analysis (PCA) of the obtained signals has allowed the discrimination of the solutions tested.     

Synthesis of a soluble conjugated copolymer based on dialkyl-substituted dithienothiophene and its application in photovoltaic cells

A soluble conjugated alternating 3,5-didecanyldithieno[3,2-b:2′,3′-d]thiophene-thiophene copolymer was synthesized by palladium(0)-catalyzed Stille coupling reaction. The thermal, absorption, emission, electrochemical, and photovoltaic properties of the polymer were examined. A weight-average molecular weight around 6.2 × 10⁴ and a polydispersity index of 1.8 was estimated for the polymer using gel permeation chromatography. The polymer exhibits good thermal stability with decomposition temperature of 340 °C and glass-transition temperature of 136 °C. The polymer shows strong absorption peaked at 505 nm in diluted solution and 518 nm in thin film with an optical band gap 2.0 eV. The polymer exhibits intense emission located at 550 nm in solution and 603 nm in film. The HOMO and LUMO energies of the polymer were estimated to be −5.4 and −3.4 eV, respectively, by cyclic voltammetry. Polymer solar cells were fabricated based on the blend of the polymer and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM). The power conversion efficiency of 0.7% was achieved under AM 1.5, 100 mW/cm² using polymer:PCBM (1:4, w/w) as active layer.     

In situ spectroelectrochemical study on a copolymer made from the 2-biphenyl-3-octylthiophene monomer

An electrically conducting copolymer film, poly(2-biphenyl-3-octylthiophene) (PBOT), was electropolymerized from the comonomer 2-biphenyl-3-octylthiophene (BOT) and characterized by both ex situ and in situ spectroelectrochemical techniques: UV-vis spectroscopy, FTIR spectroscopy and resonance Raman spectroscopy. The formed copolymer was compared with a copolymer synthesized from a mixture of 3-octylthiophene and biphenyl, poly(thienyl biphenyl) (PTB). All spectroscopic measurements gave evidence of formation of a conductive material with high content of short phenylene segments but with an effective conjugation length shorter than in the PTB copolymer film. The structure of PBOT was also less crosslinked having more para-substitution than the structure of PTB.     

Novel ZnO microflowers on nanorod arrays: local dissolution-driven growth and enhanced light harvesting in dye-sensitized solar cells

ZnO nanostructures were manipulated, via a low-temperature solution process, from pure nanorod arrays to complex nanostructures of microflowers on nanorod arrays with adjusted quantities of flowers. We proposed the mechanism of local dissolution-driven growth to rationally discuss the novel growth process. These nanostructures were used as photoanodes in dye-sensitized solar cells. Compared to pure nanorod arrays, the nanorod array-microflower hierarchical structures improved the power conversion efficiency from 0.41% to 0.92%, corresponding to a 124% efficiency increase. The enhancement of the efficiency was mainly ascribed to the synergistic effect of the enhanced surface area for higher dye loading and the improved light harvesting from efficient light scattering. Present results provide a promising route to improve the capability of light-harvesting for ZnO nanorod array-based DSSCs.     

Electrochemical and electrogravimetric behaviors of conducting polymer. Theoretical aspects and application to co-polymer films based on juglone

Redox mechanisms of conducting polymers are not yet fully understood. Attractive analytical tools and pertinent models are necessary to achieve this goal. In this paper, numerical simulations based on a theory dealing with ions transfer through electroactive film/electrolyte interface was developed to predict the behavior of a conducting polymer called poly(JUG-co-JUGA). The main advantage of this approach is that it can be applied for any polymer assuming a mixed conducting material and a thin enough film neglecting the transport effect. It is the first time where the same model allows both classical cyclic electrogravimetry (current and mass over a potential scan) and ac-electrogravimetry (electrochemical impedance and mass/potential transfer functions) to be estimated theoretically. Moreover and to our knowledge the electrochemical behavior of poly(JUG-co-JUGA) was examined through these techniques for the first time. It is shown herein that the cation transfer is preponderant but the free solvent motion must be taken into account. This effect is not detected by classical electrochemical measurements but only by combining electrochemical characterization to gravimetric measurements.     

Near-infrared light response novel shape memory actuator based on photothermal rGO-TiO2 filler

As an efficient method to realize photoinduced shape memory, photothermal filler has the characteristics of economy and convenience. However, the aggregation of the photothermal filler in the matrix material will reduce the material's shape memory and mechanical properties. In this work, the photothermal filler of reduced graphene oxide (rGO)-titanium dioxide (TiO₂) was prepared by the solvothermal method and then introduced into the polycaprolactone (PCL) matrices to construct a photoresponsive actuator. Because of TiO₂ is uniformly loaded on the rGO surface, rGO-TiO₂ disperses well in the composites. When the GO:TiO₂ ratio of photothermal filler is 1:1, the mechanical properties of PCL-GT-3 are the best, and the tensile strength and elongation at break are 31.8 MPa and 239.5%, respectively, and the crosslinking material under near-infrared light has a good photothermal effect. Due to the induced difference between the in-plane stress of the surface and the volume layer, the shape transformation can be controlled by very low energy (808 nm, 700 mW near-infrared laser). The scheme of controlling the properties of the photoinduced shape memory material by changing only the filler type is conducive to commercial application.     

Synthesis of a novel luminescent copolymer based on bisphenol A

A new luminescent copolymer (BPAEt₂‐BP; Scheme 1 ), with short alternating divinylbiphenyl units and O‐diethylated bisphenol A (BPAEt₂), was synthesized via the Wittig reaction. The polymer is fully soluble in common organic solvents and has a number‐average molecular weight of 4600 g mol^?1 with a polydispersity index of 1.79. The structure of the polymer was confirmed by ¹H NMR, ¹³C NMR, FTIR and Raman analysis. Thermal analysis of the polymer showed good stability up to 280 °C. Furthermore, polymer film absorbs at 360 nm and emits in the blue at 426 and 451 nm. The band‐gap calculated from the UV‐vis spectrum was about 2.80 eV. A single‐layer device of the configuration indium tin oxide (ITO)/BPAEt₂‐BP/Al has a relatively low turn‐on voltage of 3 V. Copyright © 2005 Society of Chemical Industry     

Gel polymer electrolytes based on a novel quaternary ammonium salt for dye-sensitized solar cells

Gel polymer electrolytes were prepared with polyacrylonitrile (PAN) and solutions of a novel quaternary ammonium salt, polysiloxane with quaternary ammonium side groups (PSQAS), in a mixture of ethylene carbonate (EC) and propylene carbonate (PC). The influences of PAN content and salt concentration on the ionic conductivity have been investigated. The ionic conductivity can be further improved with the use of the mixtures of KI and PSQAS, which can be expected as inorganic-organic salts. The gel polymer electrolytes were used in the fabrication of the dye-sensitized solar cells with a nanoporous TiO₂ working electrode, cis-di(thiocyanato)-N,N-bis(2,2-bipyridyl-4,4-dicarboxylic acid) ruthenium(II) complex dye and a counter electrode based on platinized conducting glass. The cells showed open-circuit voltages (V _oc) around 0.6 V and short-circuit current densities (J _sc) larger than 7.5 mA cm^–2 under 60 mW cm^–2 irradiation. The fill factors (FF) and energy conversion efficiencies () of the cells were calculated to be higher than 0.56 and 4.4%, respectively.     

Asphaltenes as a tackifier for hot-melt adhesives based on the styrene-isoprene-styrene block copolymer

The use of heavy crude oil asphaltenes and resins (termed asphaltenes) as the components of hot-melt adhesives based on the styrene-isoprene triblock copolymer was considered. The rheological, thermophysical, strength, and adhesive characteristics of the mixtures containing from 10 to 40 wt% of asphaltenes were studied. The addition of 10 to 20 wt% of asphaltenes enhanced the strength and adhesive properties of the mixtures and only slightly changed their rheology. The higher concentrations of asphaltenes reduced the viscosity of the mixtures but did not lead to improved characteristics of the adhesives. The ambiguous effect of asphaltenes is probably due to their uneven distribution between the microphases of the block copolymer as well as their ability to act both plasticizers and reinforcing particles depending on temperature. A comparison of asphaltenes and conventional tackifiers based on hydrocarbon resins revealed their comparable effect on the properties of the block copolymer.     

Development of a novel proton conducting fuel cell based on a Ni‐YSZ support

A new proton conducting fuel cell design based on the BZCYYb electrolyte is studied in this research. In high‐performance YSZ‐based SOFCs, the Ni‐YSZ support plays a key role in providing required electrical properties and robust mechanical behavior. In this study, this well‐established Ni‐YSZ support is used to maintain the proton conducting fuel cell integrity. The cell is in a Ni‐YSZ (375 μm support)/Ni‐BZCYYb (20 μm anode functional layer)/BZCYYb (10 μm electrolyte)/LSCF‐BZCYYb (25 μm cathode) configuration. Maximum power density values of 166, 218, and 285 mW/cm² have been obtained at 600°C, 650°C, and 700°C, respectively. AC impedance spectroscopy results show values of 2.17, 1.23, and 0.76 Ω·cm² at these temperatures where the main resistance contributor above 600°C is ohmic resistance. Very fine NiO and YSZ powders were used to achieve a suitable sintering shrinkage which can enhance the electrolyte sintering. During cosintering of the support and BZCYYb electrolyte layers, the higher shrinkage of the support layer led to compressive stress in the electrolyte, thereby enhancing its densification. The promising results of the current study show that a new generation of proton conducting fuel cells based on the chemically and mechanically robust Ni‐YSZ support can be developed which can improve long‐term performance and reduce fabrication costs of proton conducting fuel cells.     

Comparative study of polymer single cells based on sulfonated linear and star butadiene–styrene block copolymer electrolyte membranes

Proton‐conducting electrolytes based on a sulfonated hydrogenated poly(butadiene–styrene) matrix were synthesized. Block copolymer ionomers were prepared through sulfonation of part of the styrene units. The free acid samples were characterized with X‐ray photoelectron spectroscopy to quantify sulfonation. Microstructural and electrical characterizations of membranes obtained from sulfonated polymer and blends were carried out with dynamic mechanical analysis, differential scanning calorimetry, and impedance spectroscopy. Electrolytes exhibiting the highest conductivities were tested in a model hydrogen/oxygen single fuel cell working at a medium temperature range (30–80°C) and at 1 bar of pressure. The current and power densities obtained were compared with commercial Nafion electrolyte. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 367–377, 2002     

A new proton conducting membrane based on copolymer of methyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid for direct methanol fuel cells

In this paper, a new kind of copolymer methyl methacrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS-co-MMA) was synthesized by free radical polymerization. IR-spectrum and ¹H NMR were used to confirm the structure of the copolymers, and the thermal character of the copolymers was investigated with TGA and DSC. Flexible and transparent membranes based on this kind of copolymer were prepared by solution casting method. The physical properties including ionic exchange capability (IEC), water uptake, proton conductivity, methanol permeability and morphology of the membranes were investigated. These membranes showed higher water uptake though they had lower IEC compared with Nafion-117. The proton conductivity of the membrane with IEC of 0.9 mmol/g was 1.14 × 10⁻² S/cm and its methanol permeability coefficient was 5.46 × 10⁻⁷ cm²/s, much lower than that of Nafion-117. Tests on cells were also carried out to measure the performance of the membrane.     

Anhydrous proton‐conducting electrolyte based on a nematic poly(methyl acrylate) containing sulfonated side chains

A nematic poly(methyl acrylate) containing terminal sulfonic acids in side chains was prepared by etherification of a brominated mesomorphic precursor with 2‐hydroxyethanesulfonic acid sodium salt. Differential scanning calorimetry measurements and polarized light microscopy observation revealed that the sulfonated polymer exhibited the nematic mesophase at medium temperatures (189–227°C). Electrochemical impedance spectroscopy measurements showed that temperature dependence of anhydrous proton conductivity for the nematic polymer followed the Arrhenius law and that the estimated activation energy was 95 kJ mol⁻¹ in the nematic phase. The proton conductivities of the nematic polymer were two orders of magnitude higher than those of anhydrous Nafion®117 membrane at the same temperature. The enhanced anhydrous proton conductivities of the polymeric electrolyte were ascribed to the orientational order and fluidity of the nematic liquid crystal. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40382.     

Two novel d frameworks based on a new V-shaped ligand 2,4′-dipyridylamine and a flexible dicarboxylate ligand

Via hydrothermal synthesis, the self-assembly of d¹⁰ metal, 2,4′-dipyridylamine (L) and 1,3-adamantanediacetic acid (H₂ADA) generated two unprecedented coordination polymers [Zn(ADA)(L)]_n (1) and [Cd(ADA)(L)₂]_n (2). Complex 1 possesses a novel 1D looped-chain topology structure decorated with arms. Complex 2 shows an extended threaded framework involving 2D coordination layers of square (4⁴) topology with dangling ligands, which gives the novel (2D → 3D) polythreaded array. To the best of our knowledge, complex 2 is the first example with four dangling arms coordinated in the axial sites of dinuclear nodes. In addition, both of the complexes show strong photoluminescence at room temperature, and may be good candidates for potential luminescence materials.     

Proton-conducting electrolyte membranes based on hyperbranched polymer with a sulfonic acid group for high-temperature fuel cells

The hyperbranched polymers (HBP-SA-Acs) with both a sulfonic acid group as a functional group and an acryloyl group as a cross-linker at terminals in different ratios of sulfonic acid group/acryloyl group (SO₃H/Ac) were successfully synthesized as a new thermally stable proton-conducting electrolyte. The cross-linked hyperbranched polymer electrolyte membranes (CL-HBP-SAs) were prepared by thermal polymerizations of the HBP-SA-Acs using benzoyl peroxide, and their ionic conductivities under dry condition and thermal properties were investigated. The ionic conductivities of the CL-HBP-SAs were found to be in the range of 2.2 × 10⁻⁴ to 3.3 × 10⁻⁶ S/cm, depending upon the SO₃H unit contents, at 150 °C under dry condition, and showed the Vogel-Tamman-Fulcher (VTF) type temperature dependence, indicating that proton transfer is cooperated by local polymer chain motion. All CL-HBP-SAs were thermally stable up to 260 °C, and they had suitable thermal stability as electrolyte membranes for the high-temperature fuel cells under dry condition. Fuel cell measurement using a single membrane electrode assembly cell with a cross-linked electrolyte membrane was successfully performed under non-humidified condition. It was demonstrated that applying the concept of dry polymer system to proton conduction is one possible approach toward high-temperature fuel cells.     

Electrochromic properties of a novel low band gap conjugated copolymer based on 1,4-bis(2-thienyl)-naphthalene and 3,4-ethylenedioxythiophene

1,4-Bis(2-thienyl)-naphthalene (BTN) monomer is successfully synthesized via coupling reaction. A novel copolymer based on 1,4-bis(2-thienyl)-naphthalene (BTN) and 3,4-ethylenedioxythiophene (EDOT) is electrochemically synthesized and characterized. Characterizations of the resulting copolymer P(BTN-co-EDOT) are performed by cyclic voltammetry (CV), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetry (TG). At the neutral state of the copolymer, the π–π* transition absorption peak is located at 515 nm and the optical band gap (E_g) is calculated as 1.73 eV. Spectroelectrochemical analysis reveals that the copolymer film has distinct electrochromic properties from that of the BTN homopolymer film and shows six different colors under various potentials. The copolymer film shows a maximum optical contrast (ΔT%) of 48.4% at 504 nm with a response time of 0.88 s and of 45.2% at 770 nm with a response time of 0.84 s. An electrochromic device (ECD) based on P(BTN-co-EDOT) and poly(3,4-ethylenedioxythiophene) (PEDOT) is constructed and characterized. The optical contrast (ΔT%) at 645 nm is found to be 21.1% and response time is measured as 0.41 s. The coloration efficiency (CE) of the device is calculated to be 154 cm² C⁻¹ at 645 nm.