Conducting polymers: Efficient thermoelectric materials

This review highlights the recent progress made in the area of thermoelectric (TE) applications of conducting polymers and related composites. Several examples of such materials and their TE properties are discussed. TE properties of new poly(2,7‐carbazole) derivatives are highlighted. References are also made to carbon nanotube/polymer composites and their improved electrical and TE performance. Studies on polymer/inorganic materials composites have also taken a step forward and have shown very promising TE properties. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Conducting polymers in chemical sensors and arrays

The review covers main applications of conducting polymers in chemical sensors and biosensors. The first part is focused on intrinsic and induced receptor properties of conducting polymers, such as pH sensitivity, sensitivity to inorganic ions and organic molecules as well as sensitivity to gases. Induced receptor properties can be also formed by molecularly imprinted polymerization or by immobilization of biological receptors. Immobilization strategies are reviewed in the second part. The third part is focused on applications of conducting polymers as transducers and includes usual optical (fluorescence, SPR, etc.) and electrical (conductometric, amperometric, potentiometric, etc.) transducing techniques as well as organic chemosensitive semiconductor devices. An assembly of stable sensing structures requires strong binding of conducting polymers to solid supports. These aspects are discussed in the next part. Finally, an application of combinatorial synthesis and high-throughput analysis to the development and optimization of sensing materials is described.     

Conducting polymers electromechanical actuators and strain sensors

Electromechanical actuators are being investigated for a wide range of applications in medical, electronics and industrial areas. One attractive application is to incorporate conducting polymer fibre actuators into fabrics for use in prosthetic applications. In this paper, the design of polypyrrole fibre actuators for use in a glove to open and close the human hand (for assisting those with paralysis or hand injuries) is described. The key requirements for this application are the simultaneous generation of 16 mm of contractile movement and 2.9 N of force. Although not critical in the first prototypes, eventually it will also be necessary to produce a rate of movement of around 10 mm sec⁻¹. The effect of the geometry of polypyrrole actuators is examined in this paper and it is shown that a tubular geometry is superior to conventional flat films. Another aspect of the practical use of actuator materials is their control. Fabric strain gauges with polymer actuators is a convenient means for providing feedback control to the actuating element. The fabric strain gauges ideally articulate with fibre actuators to give both the actuating and sensing function in the same fabric structure.     

Conducting polymers as antennas for probing biophysical activities

Conducting polymers can serve as soft electrode substrates for anchoring and orientating functional membrane proteins. We utilize this possibility to orient bacteriorhodopsin (bR), a membrane protein that functions as a light-driven proton pump, on these substrates. The underlying polymer substrate becomes optoelectronically active with the spectral and temporal characteristics corresponding to that of the adjacent bR molecular layer. We demonstrate the concept of passive and active biomolecular signal transduction using model conducting polymers. The photoinduced current modulation in the conducting polymer layer can be explained in terms of the charge displacements within the proximal bR layer or charge-transfer processes across the interface. We explore the implications of this strong coupling between the photophysical processes in bR and electrical processes in the conducting polymer layer.     

Chemoselective reduction of 2-acyl-N-sulfonylpyrroles: synthesis of 3-pyrrolines and 2-alkylpyrroles

The partial reduction of pyrroles is not a common practice even though it offers a potential route to pyrroline building blocks, commonly used for synthesis. We have investigated the reduction of 2-acyl-N-sulfonylpyrroles and by varying the hydride source and solvent, achieved a chemoselective reduction, leading to 3-pyrrolines and alkyl pyrroles in high yield.     

Conducting polymers in redox devices and intelligent materials systems

Applications opportunities are described for conducting polymer devices, including (1) batteries and redox capacitors, (2) electromechanical actuators, (3) electrochromic windows and displays, (4) chemical separation and chemical delivery systems, and (5) indicators and sensors. Each of these potential application areas depends upon the dramatic property changes which occur during chemical or electrochemical doping. Since the properties profiles of conducting polymers can be reversibly changed either chemically or electrochemically, these polymers also provide exciting candidates for intelligent materials systems - where sensor, logic element, and actuator functions can be either partially or fully integrated. Results of device and properties investigations are used to evaluate future possibilities for conducting polymers in intelligent material systems.     

Conducting polymers in modelling transient potential of biological membranes

The possibility of using conducting polymer (CP) films doped with biological ligands as artificial biological membranes to study potential formation mechanisms is presented. Calcium and magnesium ion-binding anionic sites--asparagine, glutamine, adenosinotriphosphate and heparin are incorporated into the poly(pyrrole) film during electrochemical polymerization. This approach allows the competitive calcium-magnesium ion-exchange to be inspected by open circuit measurements. After a close-to-Nernstian sensitivity of the CP membranes was induced by soaking in alkaline solutions of calcium or magnesium, dynamic experiments were performed by a change in the bulk concentration of magnesium or calcium ions. A characteristic transitory potential response, though distinctively different for the calcium and magnesium ions, was observed and explained using the diffusion layer model (DML).     

Synthesis and properties of 1-alkoxycarbonylmethy-2-alkylpyrroles

The condensation of alkyl 2,3-dichloropropyl- and alkyl 2-methoxy-3-chloropropyl ketones with aminoacetic acid alkyl ester hydrochlorides leads to 1-alkoxycarbonylmethyl-2-alkylpyrroles. The reaction of these esters with various bases gives the corresponding 1-carbonylmethyl-2-alkylpyrroles, 1-dialkyl-aminocarbonylmethyl-2-alkylpyrroles, 1-carbazoylmethyl-2-alkylpyrroles, and potassium 2-alkylpyrrolyl-1-acetate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 769–772, June, 1993.     

New designs for sensory materials: Conducting polymers displaying molecular recognition

The integration of molecular recognition elements into conducting polymers holds great promise for the formation of new types of sensory materials. We describe some of our recent results in this area which focus on producing polymers which are responsive to alkali ions and electron deficient organic molecules.     

Conducting polymers. I. Electrical conductivity of poly(bis-p-phenylenediaminosulphoxide)

Poly(bis-p-phenylenediaminosulphoxide) was prepared by Michael addition of p-bis-N-sulphinylphenylenediamine with p-phenylenediamine at 150°C. Thermal and electrical behaviors of the polymer have been studied. The polymer is found to have increased conductivity possibly due to the participation of lone pairs of electrons on nitrogen and sulphur atoms with σ bond of the macrochain. Thermogravimetric analysis indicates that the polymer is fairly stable than other conducting polymers up to 200°C. The activation energy of the polymer was measured and found to be 13 kcal mol^?1.     

Conducting polymers VIII: Optical and electrical conductivity of poly(bis-m-phenylenediaminosulphoxide)

Poly(bis-m-phenylenediaminosulphoxide) (PPDS) was prepared from Michael addition of N,N′-bis-sulphinyl-m-phenylenediamine and m-phenylenediamine. The prepared PPDS was then doped with iodine. PPDS was characterized by FTIR, ¹H-NMR, elemental microanalysis, thermogravimetric analysis (TGA), UV-visible absorption and fluorescence emission spectra. Thermal gravimetric analysis TGA showed that PPDS is thermally stable up to 179 °C. Electronic transitions showed main absorption peak at λ = 340 nm and two emission peaks at 460 and 490 nm. The behavior of both dc and ac electrical conductivities of PPDS were studied. The direct current electrical conductivity (σ_dc) and the alternating current electrical conductivity (σ_ac) were enhanced by the physical doping of I₂ in the polymer matrix. The conduction mechanisms for dc and ac electrical conductivities have been investigated.     

Conducting carbon-nitrogen pyropolymers derived from cyanogen

Electropolymerization of cyanogen in acetonitrile containing an electrolyte yields a poly(cyanogen). Its structure involves an open-structured dimer derived from the heterocyclic anion C₇N₇? mixed with a sequence of nitrile-substituted, conjugated carbon–nitrogen bonds. Although this polymer is an insulating solid, pyrolysis in vacuo to 700°C leads to highly conducting carbon–nitrogen pyropolymers via crosslinking and nitrogen elimination. The 700° pyropolymer has a carbon–nitrogen ratio of 5:1, a room temperature conductivity of 1 Ω^?1 cm^?1, and an activation energy for conduction of ～0.03 eV.     

一维纳米纤维构筑的导电聚合物三维结构及其可控的浸润性

微/纳米结构的导电聚合物由于具有高导电性、易合成以及优异的环境稳定性从而在许多先进的研究领域备受关注,并有望在分子导线、化学和生物传感器、发光器件等领域获得广泛应用。 特别是,复杂的三维自组装结构在获得高性能和功能化的材料方面提供了巨大的潜在应用价值。本文主要介绍了我们利用胶束的软模板和自组装驱动力的协同效应,实现由一维纳米结构组装的三维微米结构导电聚合物方面的研究进展。该制备技巧在于低表面自由能的含氟有机酸具有软模板、掺杂剂、自组装驱动力,以及诱导超疏水性的多重作用实现导电聚合物三维结构的组装和多功能化。介绍了利用环境湿度调整分子的自组装驱动力,实现导电聚合物由一维纳米结构向三维微米结构的组装。此外,还介绍了利用导电聚合物可逆的化学掺杂/脱掺杂机制,实现导电聚合物表面浸润性的可逆转化。最后介绍了在液/液/固三相体系中,通过外加电场刺激,可实现油滴在导电聚合物表面的浸润性和黏附力的控制。     

Electroanalytical measurements without electrolytes: Conducting polymers as probes for redox titration in non-conductive organic media

Electroanalytical methods have been applied only in conducting media. An application of conducting polymers allows to overcome this limitation. If such material is in electrochemical equilibrium with dissolved redox active species, its electrical conductivity depends on the redox potential of these species. Therefore, conductometric measurements with conducting polymers can provide about the same information as classical redox electrodes. The approach was applied for redox titration. Equivalent points obtained by this titration in aqueous and organic electrolytes were identical. Then the approach was applied for determination of bromine number by redox titration in non-conducting organic phase.     

Ladder polymers from tetraaminodiquinoxalpyrene

A new fused aromatic heterocyclic tetraamine 2,3,11,12-tetraaminodiquinoxal [2,3-e,2′,3′-1] pyrene has been prepared and polymerized with 1,4,5,8-naphthalenetetracarboxylic acid and pyromellitic dianhydride. The resulting ladder polymers with inherent viscosities ranging from 0.5 to 1.0 dl/g in methanesulfonic acid exhibited thermal stabilities near 600°C in nitrogen and near 450°C in air.