Showing papers on "Conductive polymer published in 1995"

Template Synthesis of Electronically Conductive Polymer Nanostructures

Abstract: : Nanochemistry is an emerging subdiscipline in the chemical and materials sciences that deals with the development of methods for synthesizing nanoscopic bits of a desired material and with chemical and other investigations of the nanomaterial obtained. My research group has been exploring a general method, called "template-synthesis," for preparing nanomaterials. This method entails synthesizing the desired material within the pores of a nanoporous membrane. The membranes employed have cylindrical pores of uniform diameter. In essence, we view each of these pores as a "nanobeaker" in which a piece of the desired material is synthesized. We have used this method to prepare nanostructures composed of electronically conductive polymers, metals, semiconductors, and other materials. In this Accounts article, I discuss my work on template synthesis of electronically conductive polymer nanostructures. I will show that these conductive polymer nanostructures have interesting and unusual electronic properties and that these nanostructures provide an opportunity for exploring how molecular and supermolecular structure affect conductivity in conductive polymers.

Electrochromism : fundamentals and applications

Abstract: Part 1 Introduction: electrochromism - what is electrochromism?, existing technologies, electrochromic displays and shutters, terminology of electrochromism, primary and secondary electrochromism, colour and contrast ratio, colouration efficiency, write-erase efficiency, response time, cycle life, the insertion coefficient, ECD appearance electrochromic systems -equilibrium electrochemistry, electrochromic operation exemplified, voltammetry, charge transfer and charge transport, AC or RF electrochemistry, electrodes construction of electrochromic devices -all-solid cells with reflective operation, all-solid cells with transmissive operation, solid electrolytes, the preparation of solid electrochromic films, liquid electrolytes, self-darkening electrochromic rearview mirror for cars employing type 1 (solution-phase) electrochromes. Part 2 Electrochromic systems: metal oxides-cobalt oxide, indium tin oxide, iridium oxide, molybdenum trioxide, nickel oxide, tungsten trioxide, vanadium pentoxide, other metal oxides, mixed metal oxides, metal oxide - organic mixtures phthalocyanine compounds - lutetium bis(phthalocyanine), other metal phthalocyanines, related species prussian blue - preparation of prussian blue thin films, prussian blue electrochromic films, prussian blue ECDs, prussian blue analogues other inorganic systems - deposition of metals, deposition of colloidal material, intercalation layers, inclusion and polymeric systems bipyridilium systems - bipyridilium redox chemistry, bipyridilium species for inclusion within ECDs, recent developments electroactive conducting polymers - polyaniline electrochromes, polypyrrole electrochromes, polythiophene electrochromes, poly(carbazole), miscellaneous polymeric electrochromes, recent developments other organic electrochromes - monomeric species, tethered electrochromic species, electrochromes immobilised by viscous solvents polyelectrochromism - studies of polyelectrochromic systems photoelectrochromism and electrochromic printing - device types, electrochromic printing or electrochromography.

Micrometer- and Nanometer-Sized Polymeric Light-Emitting Diodes

Abstract: A method for the fabrication of micrometer-and submicrometer-sized polymeric light-emitting diodes is presented. Such diodes have a variety of applications. Light sources of dimensions around 100 nanometers are required for subwavelength, near-field optical microscopy. Another possible application is patterning on the micrometer and nanometer scale. The diodes have been made in the form of a sandwich structure, with the conductive polymer poly(3,4-ethylene-dioxythiophene) polymerized in the pores of commercially available microfiltration membranes defining the hole-injecting contacts, poly[3-(4-octylphenyl)-2,2;-bithiophene] as the light-emitting layer, and a thin film of calcium-aluminum as the electron injector.

Molecular-Level Processing of Conjugated Polymers. 2. Layer-by-Layer Manipulation of In-Situ Polymerized p-Type Doped Conducting Polymers

Abstract: A novel thin-film processing technique has been developed for the fabrication of ultrathin films of conducting polymers with angstrom-level control over thickness and multilayer architecture. As part 2 of this series, we present here the molecular self-assembly of p-doped conducting polymers (e.g., polypyrrole and polyaniline), a layer-by-layer process in which a substrate is alternately dipped into a chemically active aqueous solution of an in-situ polymerized conjugated polymer and a solution of a polyanion. In-situ oxidative polymerization produces continuously the highly conductive, underivatized form of the conjugated polymer, which is deposited in single layers of precisely controlled thickness as it is formed. The thickness of each layer, ranging from 20 to 60 A, can be fine-tuned by adjusting the dipping time and the solution chemistry. The surface chemistry of the substrate (hydrophobic, charged, etc.) is key in determining the deposition characteristics and uniformity of the film. Widely different deposition characteristics onto different surfaces make it possible to selectively deposit conducting polymers onto certain, well-defined regions of a substrate by patterning the surface with different chemistries. Typical multilayer films exhibit conductivities in the range of 20-80 S/cm ; however, ultrathin films with conductivities over 300 S/cm can be made with suitable adjustments to the solution chemistry.

Handbook of Solid State Batteries and Capacitors

Abstract: Mathematical Modelling of Solid State Power Sources (J-Y Chern) Silver Ion Conducting Electrolytes (T Takahashi) Copper Ion Conducting Electrolytes (R Linford) Reliability and Clinical Assessment of Pacemaker Power Sources (J Lin & E Schroeppel) Electrochemistry of Conducting Polymers (W H Smyrl) Polymer Synthesis, Properties and Performance of Solid State Polymer Electrode Cells (B Scrosati) Synthesis and Properties of Novel Ion Conducting Polymers (A G Einset & G Wnek) Spectroscopic Studies of Ion Conducting Polymers (L M Torell) Status of Polymer Electrolyte Battery Development in North America (D Fauteux) Plasticized Ambient Temperature Polymer Electrolyte Batteries (S Yde-Andersen) Solid Redox Polymerization Electrodes (S Visco). (Part contents).

Polyaniline Doped by the New Class of Dopant, Ionic Salt: Structure and Properties

Abstract: Polyaniline (PAn) can be doped through a protonation by protonic acids, in addition to an oxidation doping by Lewis acid as for the other conjugated conducting polymers. This work reports the new class of dopant, ionic salt, such as LiClO 4 , LiBF 4 , LiPF 6 , and Zn(ClO 4 ) 2 , for PAn. The ionic salt can be used to dope PAn by mixing an ionic salt with PAn in the common solvent 1-methyl-2-pyrrolidone and then casting the solution into a film. The structure and properties of ionic salt doped-PAn are investigated by UV-visible, IR and XPS spectroscopies, dynamic mechanical analysis, scanning electron microscopy, and conductivity measurement. It is found that the PAn therein is doped via pseudoprotonation of the imine nitrogen by the metal cation. As in the case of HCl-doped PAn, polarons/bipolarons are generated as reflected in the presence of UV-visible absorption peaks at 420 and 865 nm. The LiBF 4 -doped PAn film retains a conductivity at the level of 10 -2 S/cm in the temperature range 25-140 °C. The conductivity then decays to 10 -3 S/cm as temperature increases to 175 °C, resulting from the increased ring distorsion in the PAn subchains due to the glass transition.

Studies on the preparation and properties of conductive polymers. VIII. Use of heat treatment to prepare metallized films from silver chelate of PVA and PAN

Abstract: Metallized polymer films were prepared from polyacrylonitrile or poly(vinyl alcohol) silver chelate solution by heat treatment. These metallized film exhibited low surface resistivity around 100Ω/cm2. The surface of these conductive films was proved to be metallized using X-ray analysis. The metal adhered on the film was believed to be responsible for the improvement of electrical conductivity. The effects of types and concentrations of silver salt, types and volume of solvent, and drying time on the conductivity of metallized films were investigated. © 1995 John Wiley & Sons, Inc.

Electrical devices containing conductive polymers

Abstract: Electrical devices which comprise at least one metal electrode and a conductive polymer element in contact therewith, wherein the metal surface which contacts the conductive polymer has a roughened or otherwise treated surface to improve its adhesion to the conductive polymer. The metal electrode is preferably an electrodeposited foil. The conductive polymer preferably exhibits PTC behavior. The devices include heaters and circuit protection devices. The improved adhesion results in improved physical and electrical stability, and broadens the range of conductive polymer compositions which can be used in a number of important applications.

Application of conducting polymer technology in microsystems

Abstract: Conducting polymers are a new type of organic material that offer enormous potential for application within the field of microsystems. In this paper we review the basic properties of conducting polymers and discuss their application in electronic, mechanical and (bio)chemical microsystems. For instance, we have found that thin films of poly(pyrrole)/decanesulfonate have both a low friction coefficient (ca. 0.1) and wear rate (ca. 1 nm cm −1 ) that are similar to values observed for PTFE, yet possess relatively high electrical and thermal conductivities. In addition, conducting polymers can be readily electrodeposited onto planar or curved micromechanical structures, such as microslideways, micromotors or microturbines, to provide a bearing material of superior performance to standard micro-engineered materials (e.g. Si, SiO 2 , Si 3 N 4 ) and better processability than PTFE. In addition, conducting polymers can be used as gas-sensitive films in microelectronic devices. They have been shown to have a rapid, reversible ppm sensitivity to polar organic compounds (e.g. alcohols, ketones, aldehydes and fatty acids) without interference from common gases such as CO 2 , CO, CH 4 and N 2 . Conducting polymers are currently being used in commercial electronic noses, and integrated microsystems are being realised with the advent of custom microsensor array devices and application-specific integrated circuit chips.

Biosensors based on oxidases immobilized in various conducting polymers

Abstract: The electrodeposited organic polymers polypyrrole, poly(N-methylpyrrole), poly(o-phenylenediamine) and polyaniline are compared as matrices for the immobilization of glucose oxidase in the preparation of amperometric glucose biosensors. Enzyme entrapment in the polymer layer is obtained by electrodeposition of polymers from solutions of monomers containing dissolved enzyme. For all examined sensors a useful and almost linear range of response to glucose is observed up to at least 20 mM of glucose. The best sensitivity of response is obtained for a glucose sensor made of poly(o-phenylenediamine) and polypyrrole. A linear response up to 20 mM glucose is also obtained in flow-injection measurements for a glucose/polypyrrole sensor. Poly(o-phenylenediamine) is also used for satisfactory immobilization of choline oxidase in the preparation of a choline sensor, whereas a lactate biosensor has been prepared by immobilization of lactate oxidase in polypyrrole.

Comparison of the AC Impedance of Conducting Polymer Films Studied as Electrode‐Supported and Freestanding Membranes

Abstract: The ac impedance response of a symmetrically bathed membrane consisting of a conducting polymer is modeled. The model is an extension of a recent one proposed for a conducting polymer film contacting an electronic and an ionic conductor on its two faces (modified electrode geometry) and takes into account both diffusion‐migration of ionic and electronic charge carriers inside the film and charge‐transfer across metal/polymer and polymer/electrolyte interfaces. The membrane impedance is calculated for various combinations of parameters in order to stress the effect of diffusion coefficients, charge‐transfer resistance, and double layer capacitance at the interfaces. The impedance responses in the modified electrode and membrane geometries are compared. It is thus shown how some ambiguities in the attribution of certain features of the impedance of modified electrodes to either the polymer/electrode or polymer/electrolyte interfaces may be eliminated by this comparison.

Surface characterization of conducting polymer-silica nanocomposites by X-ray photoelectron spectroscopy

Abstract: The surface characterization of a range of conducting polymer-silica colloidal nanocomposites by X-ray photoelectron spectroscopy (XPS) is described. The silicon atoms in the silica component and the nitrogen atoms in the conducting polymer (polypyrrole or polyaniline) component have been utilized as unique elemental markers. Thus, measurement of the silicon/nitrogen atomic ratio by XPS allows a semiquantitative assessment of the silica/conducting polymer surface composition of the nanocomposite particles. These surface atomic ratios were then compared with the bulk silicon/nitrogen atomic ratios calculated for the nanocomposites from our macroscopic chemical composition data. We were able to confirm that, for all samples investigated, the surface composition of the conducting polymer- silica particles is silica-rich with respect to their bulk composition. These observations are consistent with the observed long-term colloidal stability ofthese dispersions. Furthermore, the surface composition of the polypyrrole-silica nanocomposites was correlated with the colloid stability of these dispersions in pH 3 and 9 buffer solutions. Finally, our XPs data confirm that, although somewhat depleted from the surface ofthe particles, the conducting polymer component is nevertheless present. This observation is consistent with the relatively high solid state electrical conductivities obtained for compressed pellets of these materials.

Electroluminescent device comprising a transparent structured electrode layer made from a conductive polymer

Abstract: A description is given of an electroluminescent (EL) device (1) composed of polymeric LEDs comprising an active layer (7) of a conjugated polymer and a transparent polymeric electrode layer (5) having electroconductive areas (51) as electrodes. Like the active layer (7), the electrode layer (5) can be manufactured in a simple manner by spin coating. The electrode layer (5) is structured into conductive electrodes (51) by exposure to UV light. The electrodes (9) and (51) jointly form a matrix of LEDs for a display. When a flexible substrate (3) is used, a very bendable EL device is obtained.

Small-Bandgap Conducting Polymers Based on Conjugated Poly(heteroarylene methines). 2. Synthesis, Structure, and Properties

Abstract: A series of soluble conjugated poly(heteroarylene methines) with varying number of 2,5-thienylene rings have been synthesized, characterized, and shown to have small intrinsic optical and electrochemical bandgaps. The conjugated polymers containing alternating aromatic and quinoid heteroarylene moieties in the main chain were prepared by oxidative dehydrogenation of precursor poly(heteroarylene methylenes) with 2,3-dicyano-5,6-dichloro-1,4-benzoquinone (DDQ). The optical and electrochemical properties of the conjugated poly(heteroarylene methines), such as bandgap, redox potentials, ionization potential, and electron affinity, were found to be significantly modified by the size of the quinoid moieties in the main chain and the type of donor or acceptor side group at the methine carbon. Some of the poly(heteroarylene methines) have intrinsic bandgaps (E g ) that are significantly smaller than found for the parent polythiophene (E g ∼ 2 eV) : PBTHBQ (E g = 1.14 eV) ; PBTBQ (E g = 1.27 eV) ; PBTTBQ (E g = 1.31 eV) ; and PBTNBQ (E g = 1.45 eV). These same four polymers have peak oxidation potentials in the range 0.29-0.54 V (SCE) and peak reduction potentials in the range -1.82 to -1.49 V (SCE). The electrical conductivity of iodine-doped thin films of PBTBQ, PBTNBQ, and PBTHBQ was 6 x 10 -3 , 2.2 x 10 -3 , and 1.6 x 10 -1 S/cm, respectively, compared to a conductivity of less than 10 -7 S/cm for the undoped materials. These results confirm that conjugated poly(heteroarylene methines) are small-bandgap conducting polymers which can be prepared by oxidative dehydrogenation of precursors.

Tuning of the Luminescence in Multiblock Alternating Copolymers. 1. Synthesis and Spectroscopy of Poly[(silanylene)thiophene]s

Abstract: Synthetic routes to alternating copolymers consisting of oligosilylene blocks and oligothiophene blocks (T-x; x = 1, 2, 3, 4, or 6 rings) are presented. Solubility requirements for obtaining acceptable molecular weights and, eventually, for film formation are met by the introduction of butyl groups replacing methyls on the silicon atoms and by employing T-6 blocks carrying two octyl substituents. Additionally, substituted oligothiophenes are synthesized as an aid in the interpretation of NMR, absorption, and fluorescence spectra. Regarding the electronic configuration of the oligothiophene blocks, NMR spectra show clear differences between plain oligothiophenes, end-substituted oligothiophenes, and polymers, indicative of pi-sigma interactions with the oligosilylene blocks and possible through-conjugation to adjacent blocks in polymers. Red shifts in optical spectra show a parallel trend across the various compounds based on the same oligothiophene unit, related to the stabilization of photoexcited states on the oligothiophene by the oligosilylene substituents. These effects are strong in T-2-based compounds and reduced fdr longer T-n. The main feature of the spectra is the decrease of the transition energies with the size of the oligothiophene blocks in the polymers. Since this effect is also found in fluorescence, it enables one to adjust the luminescence wavelength by choosing the proper block length (''chemical tuning''). Fluorescence quantum efficiencies in solution are found to be remarkably high in polymers based on T-2 blocks. Spin-coated films of T-2-based (or T-3-based) polymers show evidence of T-4 (T-6) impurity blocks that act as an exciton trap.

Polymer Films on Electrodes. 26. Study of Ion Transport and Electron Transfer at Polypyrrole Films by Scanning Electrochemical Microscopy

Abstract: The oxidation and reduction of the conductive polymer polypyrrole (PPy) doped with different counterions (bromide, ferrocyanide (FCN) and poly@-styrenesulfonate)) was studied by scanning electrochemical microscopy (SECM) during both potential step (chronocoulometric) and cyclic voltammetric scans. The ultramicroelectrode tip was positioned, close to the surface of a PPy-modified substrate electrode, and the responses of both electrodes to a substrate potential step or linear sweep were monitored simultaneously. In this way, the rates of bromide or ferrocyanide ejection during PPy reduction were shown to be functions of the reduction potential. The nature of the cation (e.g., TBA+ vs K+) was an important factor determining the kinetics of ion transport in the PPy+/FCN- films. With a solution containing TBA+ the release of Fe(CN)64during PPy+/FCN- reduction was kinetically slow, and some ferrocyanide-containing species were also ejected during film reoxidation. Direct evidence for the incorporation of cations (e.g., RU(NH~)~~/~+) in a PPy film during its reduction was also obtained by SECM measurements. Finally, the physical localization and mechanism of Fc+ (Fc = ferrocene) and O~(bpy)3~+ (bpy = 2,2’-bipyridine) reduction at oxidized and reduced PPy are discussed in connection with the applicability of different models for conducting polymers.

Proton conducting polymers

Abstract: The subject invention relates to solid polymer electrolyte membranes comprising proton conducting polymers stable at temperatures in excess of 100 °C, the polymer being basic polymer complexed with a strong acid or an acid polymer. The invention further relates to the use of such membranes in electrolytic cells and acid fuel cells. Particularly, the invention relates to the use of polybenzimidazole as a suitable polymer electrolyte membrane.

High charge density conducting polymer/graphite fiber composite electrodes for battery applications

Abstract: Novel composite electrode structures have been fabricated by single-step electropolymerization of polypyrrole onto a porous graphite fiber matrix. The graphite substrate provides a lightweight structure with high surface area. The available charge capacity of the composite electrodes was proportional to the electropolymerization time and the mass of electroactive polymer with reversible charge capacities in excess of 4.0 C/cm{sup 2} and a specific capacity of 90 mAh/g, independent of polymer mass. The rate of charge extraction was dependent on the polymer mass and the morphology of the polymer electrode. In test cells using a polypyrrole/graphite fiber anode and a polypyrrole-polystyrene sulfonate/graphite fiber cathode, the authors have demonstrated a capacity of more than 40 mAh/g based on the active mass of the undoped polymer on discharging the cell to 0.1 V over a 10 k{Omega} load. More than 70% of the available charge was extracted from the cell over 50 cycles with no degradation of cell performance.

Template Synthesis of Electronically Conductive Polymer Nanostructures

Abstract: : Nanochemistry is an emerging subdiscipline in the chemical and materials sciences that deals with the development of methods for synthesizing nanoscopic bits of a desired material and with chemical and other investigations of the nanomaterial obtained. My research group has been exploring a general method, called "template-synthesis," for preparing nanomaterials. This method entails synthesizing the desired material within the pores of a nanoporous membrane. The membranes employed have cylindrical pores of uniform diameter. In essence, we view each of these pores as a "nanobeaker" in which a piece of the desired material is synthesized. We have used this method to prepare nanostructures composed of electronically conductive polymers, metals, semiconductors, and other materials. In this Accounts article, I discuss my work on template synthesis of electronically conductive polymer nanostructures. I will show that these conductive polymer nanostructures have interesting and unusual electronic properties and that these nanostructures provide an opportunity for exploring how molecular and supermolecular structure affect conductivity in conductive polymers.

Special Polymers for Electronics and Optoelectronics

Abstract: Conductive polymers. Electrodepositable resists. Polymeric Langmuir-Blodgett films. Nonlinear materials. Ferroelectric polymers. Electroactive composites. Thermotropic liquid crystal polymers. Photoconductive polymers. Polymers for optical data storage. Index.