Showing papers on "Conductive polymer published in 2003"

Conducting polymers in electronic chemical sensors.

Abstract: Conducting organic polymers have found two main kinds of application in electronics so far: as materials for construction of various devices and as selective layers in chemical sensors. In either case, interaction with ambient gases is critical. It may compromise the performance of a device based on conducting polymers, whereas it is beneficial in a sensor. Conductivity has been the primary property of interest. Work function--related to conductivity, but in principle a different property--has received only scant attention. Our aim here is to discuss the usability of conducting polymers in both types of electronic applications in light of these two parameters.

Method for producing conductive polymer, conductive polymer, conductive polymer molding and conductive molymer, laminate and apparatus using them

Abstract: PROBLEM TO BE SOLVED: To provide a method for producing a conductive polymer, obtain the conductive polymer, provide a molding and a laminate of the conductive polymer, and an apparatus using the molding and the laminate of the conductive polymer. SOLUTION: The method for producing the conductive polymer is to produce the conductive polymer having stretchability through electrochemical reduction by electrolytic polymerization. In the electrolytic polymerization, an electrolyte containing trifluoromethanesulfonic acid ion and/or anion containing two or more fluorine atoms to a central atom is used and a metal electrode is used as an action electrode for forming the conductive polymer. COPYRIGHT: (C)2004,JPO

Photovoltaic cells made from conjugated polymers infiltrated into mesoporous titania

Abstract: We have made photovoltaic cells by infiltrating the conjugated polymer regioregular poly(3-hexylthiophene) into films of mesoporous titania, which are self-assembled using a structure directing block copolymer. The mesoporous titania films were chosen because they have pores with a diameter slightly less than 10 nm, which is the exciton diffusion length in many conjugated polymers, and because they provide continuous pathways for electrons to travel to an electrode after electron transfer has occurred. The photovoltaic cells have an external quantum efficiency of 10% and a 1.5% power conversion efficiency under monochromatic 514 nm light. Experiments that vary the amount of polymer in the titania films suggest that the performance of the cells is limited by poor hole transport in the polymer.

Size-tunable infrared (1000–1600 nm) electroluminescence from PbS quantum-dot nanocrystals in a semiconducting polymer

Abstract: Nanocomposites consisting of PbS nanocrystals in a conjugated polymer matrix were fabricated. We report results of photo- and electroluminescence across the range of 1000 to 1600 nm with tunability obtained via the quantum-size effect. The intensity of electroluminescence reached values corresponding to an internal quantum efficiency up to 1.2%. We discuss the impact of using different-length capping ligands on the transfer of excitations from polymer matrix to nanocrystals.

Organic photovoltaics : concepts and realization

Abstract: 1 Photoinduced Charge Transfer in Bulk Heterojunction Composites.- 2 Optical and Spectroscopic Properties of Conjugated Polymers.- 3 Transport Properties of Conjugated Polymers.- 4 Quantum Solar Energy Conversion and Application to Organic Solar Cells.- 5 Semiconductor Aspects of Organic Bulk Heterojunction Solar Cells.- 6 Organic Photodiodes: From Diodes to Blends.- 7 Dye-Sensitized Solar Cells.

Electrospun polyaniline/polyethylene oxide nanofiber field-effect transistor

Abstract: We report on the observation of field effect transistor (FET) behavior in electrospun camphorsulfonic acid doped polyaniline(PANi)/polyethylene oxide(PE0) nanofibers. Saturation channel currents are observed at surprisingly low source/drain voltages. The hole mobility in the depletion regime is 1.4 x 10(exp -4) sq cm/V s while the 1-D charge density (at zero gate bias) is calculated to be approximately 1 hole per 50 two-ring repeat units of polyaniline, consistent with the rather high channel conductivity (approx. 10(exp -3) S/cm). Reducing or eliminating the PEO content in the fiber is expected to enhance device parameters. Electrospinning is thus proposed as a simple method of fabricating 1-D polymer FET's.

Anhydrous proton-conducting polymers

Abstract: ▪ Abstract Anhydrous proton-conducting polymers usually consist of a more or less inert polymer matrix that is swollen with an appropriate proton solvent (in most cases, phosphoric acid). An outline of the different materials is provided, with a focus on PBI/H3PO4 blends that are currently most suitable for fuel cell applications. Also discussed are alternative concepts for fully polymeric materials, which establish proton conductivity as an intrinsic property using amphoteric heterocycles such as imidazole as a proton solvent. The development of some of the first polymers is described, and the fundamental relations between their material properties and conductivity are discussed. Closely related to this relatively new concept are mechanistic investigations focusing on intermolecular proton transfer and diffusion of (protonated) solvent molecules, the contributions of both transport processes to conductivity, and the dependence of these ratios on composition, charge carrier density, etc. Although the deve...

Electrochemical and XPS studies toward the role of monomeric and polymeric sulfonate counterions in the synthesis, composition, and properties of poly(3,4-ethylenedioxythiophene)

Abstract: Electrochemically prepared poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrenesulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, was characterized by cyclic voltammetry CV, UV−vis spectroscopy, in situ conductivity, and XPS spectroscopy and was compared with electrochemically prepared PEDT/tosylate and chemically prepared PEDT/PSS. CV analysis shows that the polymer synthesis is strongly affected by the nucleophilic character of the counteranion. Although CV and UV−vis spectroscopy show that the structure and degree of polymerization (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS is able to explain the different conductivity values for these materials (ranging from 1 S cm-1 for PEDT/PSSNa to 400−450 S cm-1 for PEDT/tosylate) based on doping level and composition. In particular, critical results are observed to be the ratios between sulfonate and thiophene units in the polymers: the higher the PEDT concentration, the higher the conductivity. XPS al...

Ionic conductivity in the crystalline polymer electrolytes PEO6:LiXF6, X = P, As, Sb.

Abstract: Ionically conducting polymers (salts dissolved in a polymer matrix) are of great interest because they uniquely exhibit ionic conductivity in a soft but solid membrane. As such, they are critical to the development of devices such as all-solid-state lithium batteries. The established view of ionic conductivity in polymer electrolytes is that this occurs in amorphous materials above their glass transition temperature and that crystalline polymer electrolytes are insulators. In contrast, we show that three crystalline polymer electrolytes, poly(ethylene oxide)(6):LiXF(6), X = P, As, Sb, not only conduct but do so better than the analogous amorphous phases! It is also shown that the conductivities of all three 6:1 complexes are similar, consistent with the dimension of the bottlenecks to conduction derived from their crystal structures. An increase in ionic conductivity with reduction of molecular weight of the crystalline polymer electrolyte (from 2000 to 1000) is reported and shown to relate to the increase in crystallite size on reducing molecular weight.

High-contrast electrochromism from layer-by-layer polymer films

Abstract: Layer-by-layer (LBL) assembly is the ideal processing technique to combine two electrochromic polymers into a single thin film composite with fine control over morphology and composition. Here we present a very-high-contrast electrochromic composite developed from the LBL assembly of two readily available cathodically coloring electrochromic polymers: poly(hexyl viologen) (PXV) and the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:SPS) colloid. Characterization of assembly reveals that film thickness increases exponentially with increasing layer-pair number, seemingly due to the globular nature of the PEDOT:SPS colloid. Elemental analysis confirmed the presence of both polymers in the final film and allowed the determination of a bulk composition profile. In detailed electrochemical and spectral investigations, the “dual electrochrome” was compared to single-electrochrome LBL films, confirming that both polymers contribute to electrochromic switching. Due to the unusual film architectur...

Oligofluorene−Thiophene Derivatives as High-Performance Semiconductors for Organic Thin Film Transistors

Abstract: A series of alkyl chain end-capped oligofluorene−thiophenes have been prepared with high yields using Suzuki or Stille coupling reactions. The electronic and optical properties of the thin films deposited at different substrate temperatures have been investigated. Morphological studies using transmission electron microscopy (TEM) revealed well-interconnected microcrystalline domains in these thin films. X-ray diffraction measurements of the vacuum-evaporated films showed enhanced crystalline order with increasing substrate deposition temperature. Thermal analysis as well as electrochemical measurements of the materials indicated that the new oligomers have high thermal and oxidative stability. Highly ordered polycrystalline vacuum-evaporated films with charge carrier mobility as high as 0.12 cm2 V-1 s-1 have been achieved with 5,5‘-bis(7-hexyl-9H-fluoren-2-yl)-2,2‘-bithiophene (DHFTTF). Thin film field-effect transistor (TFT) devices made from these materials showed remarkable stability even after UV (366...

Inkjet Printing of Light-Emitting Polymer Displays

Abstract: Based on the concept of a microliquid process, we have developed an organic electroluminescent display using conductive polymers, including light-emitting polymers. The technology of inkjet printing has progressed enough to be used for the microliquid process. First, we describe the process used to form a patterned thin film. This involves inkjet-related technologies, the self-patterning behavior of a microliquid on the substrate, and the drying process that defines the thickness profile and film properties. Some microliquid behaviors and related phenomena, along with properties of the resulting film, were identified as distinct from those coming from a macroscopic liquid, as a result of size effects. By fully utilizing these unique properties of microliquids, we have succeeded in fabricating color-pixel arrays by direct patterning of polymer solutions. As a result, an organic electroluminescent display with a vivid full-color image has been developed.

Biosensors Based on Aligned Carbon Nanotubes Coated with Inherently Conducting Polymers

Abstract: The use of multiwalled aligned carbon nanotubes provides a novel electrode platform for inherently conducting polymer based biosensors. The example used here to highlight the usefulness of such a platform is the polypyrrole based glucose oxidase system for detection of glucose. The use of these three dimensional electrodes offers advantages in that large accessible enzyme loadings can be obtained within an ultrathin layer. It has also been found that the detection of H2O2 at these new electrode structures containing iron loaded nanotube tips can be achieved at low anodic potentials. The result is a sensitive and selective glucose sensor.

Adsorbed surfactants as templates for the synthesis of morphologically controlled polyaniline and polypyrrole nanostructures on flat surfaces: from spheres to wires to flat films.

Abstract: Nanostructures of polyaniline (PAni) and polypyrrole (PPy) with controlled morphologies have been synthesized on atomically flat surfaces using adsorbed surfactant molecules as templates. Atomic force microscopy (AFM) has been used to investigate polymer film formation on highly oriented pyrolytic graphite (HOPG) and chemically modified HOPG. Morphological control over the resulting polymer film is possible by the addition of coadsorbing molecules, manipulation of the length of the surfactant hydrophobe, or by changing the surface chemistry of the adsorbing substrate. Phase transitions between spheres, cylinders/wires, and featureless films have been observed which exactly parallel transitions between spheres, cylinders, and flat layers in the adsorbed surfactant. Parallel arrays of PAni nanowires can be synthesized with alignment evident over large areas in a simple self-assembly technique in which fabrication and arrangement take place simultaneously. Such a technique in which one can engineer sub-100-nm-ordered nanoscale pi-conjugated polymer structures of a desired shape by a simple self-assembly process presents potential as templates, sensors, and microelectronic devices.

Potentiometric Ion Sensors Based on Conducting Polymers

Abstract: Conducting polymers (electroactive conjugated polymers, ECPs) have emerged as one of the most promising transducers for chemical sensors. This is related to the unique electrical, electrochemical and optical properties of conjugated polymers that can be used to convert chemical information (concentration, activity, partial pressure) into electrical or optical signals in the solid state. Application of conjugated polymers in potentiometric ion sensors (ion-selective electrodes, ISEs) is reviewed.

High-dielectric-constant all-polymer percolative composites

Abstract: We report here an all-polymer high-dielectric (dielectric constant K>1000 at 1 kHz) percolative composite material, fabricated by a combination of conductive polyaniline particles (K>105) within a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymer matrix (K>50). These high-K polymer hybrid materials also exhibit high electromechanical responses. For example, 1.5% strain, which is proportional to the square of the field applied, can be induced by a field of 9.5 MV/m, an eightfold reduction in field applied compared with that in a fluoroterpolymer matrix.

Polyaniline and Carbon Nanotubes Based Composites Containing Whole Units and Fragments of Nanotubes

Abstract: Using surface-enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopy, we show that composites based on polyaniline (PANI) and single-walled carbon nanotubes (SWNTs) are different when they are prepared by two different methods: (1) by adding dispersed SWNTs to the polymer solutions and (2) by chemical polymerization of aniline in the presence of SWNTs. The difference originates from the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs into fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FTIR spectra of the composites PANI/SWNTs and PANI/C60 chemically prepared. All compounds exhibit an absorption band at 1144 cm-1 in their FTIR spectra, increasing with the carbon nanoparticules content, as a signature of a charge transfer between the constituents. Besides, the FTIR spectrum of the compounds obtained by adding SWNTs to the polymer...

Templateless Assembly of Molecularly Aligned Conductive Polymer Nanowires: A New Approach for Oriented Nanostructures

Abstract: Although oriented carbon nanotubes, oriented nanowires of metals, semiconductors and oxides have attracted wide attention, there have been few reports on oriented polymer nanostructures such as nanowires In this paper we report the assembly of large arrays of oriented nanowires containing molecularly aligned conducting polymers (polyaniline) without using a porous membrane template to support the polymer The uniform oriented nanowires were prepared through controlled nucleation and growth during a stepwise electrochemical deposition process in which a large number of nuclei were first deposited on the substrate using a large current density After the initial nucleation, the current density was reduced stepwise in order to grow the oriented nanowires from the nucleation sites created in the first step The usefulness of these new polymer structures is demonstrated with a chemical sensor device for H(2)O(2), the detection of which is widely investigated for biosensors Finally, we demonstrated that controlled nucleation and growth is a general approach and has potential for growing oriented nanostructures of other materials