Showing papers on "Conductive polymer published in 1994"

Electrically conducting polymers can noninvasively control the shape and growth of mammalian cells.

Abstract: Electrically conducting polymers are novel in that their surface properties, including charge density and wettability, can be reversibly changed with an applied electrical potential. Such properties might render conducting polymers unique for biological applications. However, the majority of research on conducting polymers has been carried out under nonbiological conditions. We synthesized optically transparent polypyrrole thin films and studied them in environments suitable for protein adsorption and mammalian cell culture. In vitro studies demonstrated that extracellular matrix molecules, such as fibronectin, adsorb efficiently onto polypyrrole thin films and support cell attachment under serum-free conditions. When aortic endothelial cells were cultured on fibronectin-coated polypyrrole (oxidized) in either chemically defined medium or the presence of serum, cells spread normally and synthesized DNA. In contrast, when the polymer was switched to its neutral state by applying an electrical potential, both cell extension and DNA synthesis were inhibited without affecting cell viability. Application of a similar electrical potential to cells cultured on indium tin oxide surfaces had no effect on cell shape or function. These data suggest that electrically conducting polymers may represent a type of culture substrate which could provide a noninvasive means to control the shape and function of adherent cells, independent of any medium alteration.

Electromagnetic radiation shielding by intrinsically conducting polymers

Abstract: The shielding efficiency of various intrinsically conducting polymers (ICPs) as a function of their intrinsic properties (conductivity and dielectric constant), thickness, and temperature is determined. Two types of shielding, reflection and absorption, by ICPs are discussed. The high shielding efficiencies of highly conducting doped polyaniline, polypyrrole, and polyacetylene are reported and compared to that of copper. The easy tuning of intrinsic properties by chemical processing suggests the wide applications of ICPs, especially polyaniline for shielding.

Toward real applications of conductive polymers

Abstract: The chemical polymerization of pyrrole in the presence of textile substrates results in the formation of electrically conducting, polypyrrole coated fabrics. Applications of these materials include microwave attenuation, static charge dissipation, and EMI shielding. The degradation kinetics of the electrical conductivity of these materials has been investigated and found to proceed by multiple rate laws. In the initial stages of conductivity loss, a diffusion controlled mechanism predominates, where oxygen diffusion into the polypyrrole film is rate limiting. At longer times, the degradation follows a simple first-order decay. The dopant anion employed during polymerization has a profound influence on the stability of the resulting film, and SEM analysis indicate that film morphology plays an important role in this effect. In the absence of oxygen, conductivity loss is significantly slower and displays a strong dependence on chloride content.

Proton conducting polymers used as membranes

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.

Solid electrolytic capacitor and method for manufacturing the same

Abstract: A solid electrolytic capacitor using a conductive polymeric compound as a solid electrolyte is disclosed, wherein a powder is dispersed in the conductive polymer to provide unevenness on the surface of the solid electrolyte, thereby increasing the surface area, whereby a mechanical adhesion between the solid electrolyte and a cathode conductor layer is increased. The conductive polymer comprises a first conductive polymer layer which contacts a dielectric layer at an anode body side, and a second conductive polymer layer which contacts the cathode conductor layer side, and the powder is dispersed in the second conductive polymer layer. By this constitution, tan δ and an equivalent series resistance (ESR) of the solid electrolytic capacitor are decreased.

Organic conductors : fundamentals and applications

Abstract: Organic Conductors: An Overview. Basic Physical Concepts of Organic Conductors. Molecular Design of Organic Conductors. Chemical Synthesis and Crystal Growth Techniques. Organic Conductors: The Crystallographic Approach. Optical Properties. Magnetic, ESR, and NMR Properties. Organic Semiconductors. Organic Metals. Organic Superconductors: From (TMTSF)2PF6 to Fullerenes. Introduction to Conjugated and Conducting Polymers. Undoped (Semiconducting) Conjugated Polymers - From Structure and Electronic Properties to Applications. Doped Conjugated Polymers: Conducting Polymers. Related Topics I: Charge-Transfer Complexes in Biological Systems. Related Topics II: Thallium-Based High-T, Superconducting Oxides: A Summary. Applications of Organic Conductors: Molecular Electronics. Organic Photoconductors and Photovoltaics.

Counter-ion induced processibility of polyaniline: conducting melt-processible polymer blends

Abstract: Summary form only given. Conducting polymer blends made by blending thermoplastic bulk polymers with Polarene/sup TM/, a proprietary conducting polyaniline composition, using conventional melt-processing techniques are reported. The percolation threshold for conductivity is observed at astonishingly low weight fractions of the conjugated conducting polyaniline indicating the formation of a unique morphology. Results on electrical and mechanical properties of these blends will be presented and discussed.

Towards an integrated electronic nose using conducting polymer sensors

Abstract: This paper describes progress that has been made towards realizing an artificial nose based on arrays of conducting polymers. Electrically conducting organic polymers based on heterocyclic molecules display reversible changes in conductivity when exposed to polar volatile chemicals. In the sensor described, the polymers are interrogated for resistance changes by means of an application-specific integrated circuit (ASIC) realized in BiCMOS technology. The ASIC and the polymer array are housed on a single thick-film ceramic substrate.

Waterborne core-shell dispersions based on intrinsically conducting polymers for coating applications

Abstract: Summary form only given. A new route to obtain waterborne colloidal dispersions of intrinsically conducting polymers is found. A commercial aqueous resin dispersion which is stabilized by non-ionic surfactants is used and aqueous solutions of oxidant, eg FeCl/sub 3/, and pyrrole are added. The polypyrrole resin dispersion is centrifuge to remove excess oxidant and redispersed in water. Instead of pyrrole, aniline can be used. Reaction conditions like concentration, temperature and type of oxidant are varied. Core-shell like particles are shown to exist in polypyrrole/alkyd and, polypyrrole/polyurethane dispersions by microelectroforesis and dielectric measurements. It is believed that these were formed by polymerization of pyrrole at the water/resin interface. The polypyrrole shells can easily form a conducting path in the coating. Coatings from these dispersions have good conductivity and stability depending on the reaction conditions.

Molecular self-assembly of electrically conductive polymers

Abstract: A molecular self-assembly process based on the alternating deposition of a p-type doped electrically conductive polycationic polymer and a conjugated or nonconjugated polyanion or water soluble, non-ionic polymer has been developed. In this process, monolayers of electrically conductive polymers are spontaneously adsorbed onto a substrate from dilute solutions and subsequently built-up into multilayer thin films by alternating deposition with a soluble polyanion or water soluble, non-ionic polymer. In contrast to a deposition process involving the alternate self-assembly of polycations and polyanions, this process is driven by non-covalent bonded attractions (for example, ionic and hydrogen bonds) developed between a p-type doped conducting polymer and a polymer capable of forming strong secondary bonds. The net positive charge of the conducting polymer can be systematically adjusted by simply varying its doping level. Thus, with suitable choice of doping agent, doping level and solvent, it is possible to manipulate a wide variety of conducting polymers into exceptionally uniform multilayer thin films with layer thicknesses ranging from a single monolayer to multiple layers.

Method of manufacturing a pattern of an electrically conductive polymer on a substrate surface and method of metallizing such a pattern

Abstract: A solution of monomers, oligomers or polymers and a suitable oxidation agent can be stable if the solution also comprises a base. By spin coating this solution onto a substrate, a layer can be formed which, after patterned irradiation, yields a pattern of a doped conductive polymer which is formed in situ, the exposed and unexposed areas exhibiting a large difference in conductivity. A description is given of, inter alia, the patterned irradiation of a layer of 3,4-ethylenedioxythiophene. If desired, the conductive polymer pattern can subsequently be metallized in an electroplating bath. The method provides, inter alia, a simple process of manufacturing metal patterns on insulating substrates, such as printed circuit boards.

Microwave properties of conductive polymers

Abstract: Conductive polymers are a new class of microwave absorbing materials which show a number of advantages over traditional granular material. Polypyrrole, Polyaniline, and Polyalkylthiophenes can be applied in specific fields where the conductive inclusion is directly integrated in the matrix or on the substrate (honeycomb, textile) during systhesis, instead of being mechanically dispersed as in the case of extrinsic conductive materials. This method can be used to produce materials with specific properties, whose performances are equivalent to those of magnetic materials but with lower surface mass. The properties of these materials can be easily modified by chemical means and by tailoring the structural properties. We show that dielectric properties strongly depend on the microstructure of conductive polymer. For that purpose, the influence of the molecular weight, density of defects, size of the alkyl chain on the substituted monomer and nature of counter anion have been explored. A theoretical models using physicochemical properties of polymer have been developed in order to calculate the frequency dependence of (e′, e″) with for a chain of Polyaniline.