Showing papers on "Conductive polymer published in 1991"

EMI shielding measurements of conductive polymer blends

Abstract: Shielding efficiencies for a number of blends containing a variety of conductive fillers, including intrinsically conductive polymers, have been measured in the near field with a dual-chamber box and in the far field with a transmission line fixture. Although all samples satisfied the classical good-conductor approximation, most of them exhibited a crossover from being electrically thin (thickness skin depth) over the frequency range of interest, 1 MHz to 3 GHz. The theoretical relations for both near-field and far-field shielding which are prevalent in the literature do not accurately describe this region of crossover. The authors have derived expressions which describe the behavior accurately over the entire range of interest. Far-field shielding efficiencies as high as 70 dB at 1 GHz were measured for purely organic composites consisting of an intrinsically conductive polymer, polyaniline, dispersed in a thermoplastic matrix. >

Handbook of polymer synthesis

Abstract: Polyefins. Polystyrenes and Other Aromatic Poly(Vinyl Compounds). Poly(vinyl ehters)s Poly (vinyl ester)s, and Poly (vinyl halogenide)s. Polymers of Acrylic Acid, Methacrylic Acid, Maleic Acid, and Their Derivatives. Polymeric Dienes. Metathesis Polymerization of Cycloolefins. Aromatic Polyethers. Polyurethanes. Polymides. Poly(vinyl aldehyde)s, Poly(vinyl ketone)s, and Phosphorous-Containing Vinyl Polymers. Metal-Containing Macromolecules. Electrically Conducting Polymers. Photoconductive Polymers. Polymers for Organic Light Emitting Devices/Diodes (OLEDS). Crosslinking and Polymer Networks. Biodegradable Polymers for Biomedical Applications. Controlled/Living Radical Polymerization.

“Synthetic metals”: A novel role for organic polymers

Abstract: The synthesis and p- and n-doping of polyacetylene, (CH)x, the prototype conducting polymer or “synthetic metal” is described together with a qualitative description of its band structure and changes in band structure on doping to yield positive and negative solitons. Other conducting polymers are briefly discussed. The polyanilines, a large class of versatile conducting polymers involving a novel non-redox doping process, considered as being of significant commercial technological importance are discussed in particular with reference to their ease of processing. Present and future technological uses of conducting polymers are noted.

Quartz Crystal Microbalance Study: Ionic Motion Across Conducting Polymers

Abstract: In situ monitoring of mass change was performed during electrochemical growth and redox cycling of a conducting polymer(polypyrrole) on a quartz crystal microbalance. For the polypyrrole films grown with large polymeric anions(poly(4-styrenesulfonate) and polyvinylsulfonate), mostly cations and solvent molecules were inserted and removed to compensate charge in polypyrrole. The films formed with medium-sized anions (tosylate) showed both apparent anion and cation motion during the redox process. The films prepared in the presence of small anions (ClO 4 − and BF 4 − ) showed mostly anion motion, but apparent cation motion also became significant for higher oxidation and/or reduction state

Conductive sensors and their use in diagnostic assays

Abstract: A conductive sensor and its use in a diagnostic assay are disclosed. The miniaturized conductive sensor, utilizing a conducting polymer, is used in a diagnostic device to determine the presence or concentration of a predetermined analyte in a liquid test sample, wherein the predetermined analyte, like glucose, is assayed by an oxidase interaction. The interaction between the oxidase and a small amount of the predetermined analyte in the test sample generates, either directly or indirectly, a dopant compound in a reaction zone of the conductive sensor. The dopant compound then migrates to the detection zone of the conductive sensor of the diagnostic device to oxidize the conducting polymer and convert the conducting polymer from an insulating form to a conducting form. The resulting increase in conductivity of the conducting polymer is measured, then the conductivity increase is correlated to the concentration of the predetermined analyte in the test sample.

XPS study of self-doped conducting polyaniline and parent systems

Abstract: The structure and protonation level of sulfonated polyaniline as well as the chemically synthesized emeraldine base and its chloride salt have been investigated. The XPS results indicate that ∼ 50% of the phenyl rings of the sulfonated polyaniline have a hydrogen atom substituted by a -SO 3 H group. Approximately 50% of the nitrogen sites are protonated in this self-doped conducting polymer. The protonation level remains unchanged upon exposure to high vacuum at room temperature. In contrast, emeraldine hydrochloride undergoes partial deprotonation and probably reduction as well under high-vacuum conditions

Three dimensionality of ``metallic'' states in conducting polymers: Polyaniline

Abstract: Anisotropic-conductiity (\ensuremath{\sigma}), thermopower, and dielectric-constant studies show that oriented polyaniline salt is representative of a class of quasi-one-dimensional disordered conductors where coupled parallel chains form ``metallic'' bundles in which electron wave functions are extended three dimensionally. This is in contrast to isolated conducting chains in conventional 1D conductors. The bundles correspond to crystalline regions of the polymer. The results are important for understanding the stabilization of metallic states and achievement of high \ensuremath{\sigma} in conducting polymers.

Molecular and Supermolecular Origins of Enhanced Electronic Conductivity in Template-Synthesized Polyheterocyclic Fibrils. Part 1. Supermolecular Effects

Abstract: : The pores in a nanoporous membrane can be used as templates for the synthesis of nanostructures. We have recently shown that conductive polymer fibrils, obtained via this template synthetic method, can show dramatically higher electronic conductivities than conventional versions of the analogous polymers. In this and a succeeding paper we explore the molecular and supermolecular origins of this enhanced electronic conductivity. This paper focuses on supermolecular effects. We have used DC and optical measurements of conductivity, X-ray diffraction, and polarized infrared absorption spectroscopy to show that the polymer chains in the narrowest template-synthesized fibrils are preferentially oriented parallel to the axes of these fibrils. This preferential polymer chain orientation is partially responsible for the observed conductivity enhancements. We also show that template-synthesis can yield poly(3-methylthiophene) fibrils with conductivities as high as 6600 S cm-1. This is the highest conductivity ever reported for a heterocyclic polymer.

Conducting polymer composites

Abstract: Electrically conducting polypyrrole coatings on inorganic cores were obtained by deposition of pyrrole on catalytically active particles. The finely dispersed core materials were hematite (polyhedral and spindle-type), silica coated with hematite, and cerium(IV) oxide. The degree of polymer coverage could be controlled by varying the aging time and the properties of the carrier particles. The so prepared coated powders were examined by transmission electron microscopy and further characterized by elemental and thermogravimetric analyses, as well as by electrophoresis, X-ray diffraction, and conductivity measurements. The conductivities were comparable to those reported for pure polypyrrole and they increased with pressure.

Measurement of the microwave conductivity of a polymeric material with potential applications in absorbers and shielding

Abstract: The microwave conductivity of a new material, the polymer poly-p-phenylene-benzobis-thiazole (PBT) made conductive by ion-implantation doping with iodine, is measured at 9.89 GHz as a function of temperature using the cavity perturbation technique applicable to thin films of arbitrary shape. The DC and microwave conductivities of PBT are seen to approach asymptotically the low-temperature limit predicted by Mott's energy-dependent hopping model. The potential utilization of conductive polymers in microwave absorbers and electromagnetic interference (EMI) shielding is examined using layered media EM theory. >

Analytical applications of conducting polymers

Abstract: An overview of the analytical applications of conducting polymers is given. Examples of methods based on the change in electrically conductivity of the polymer membrane, exchange of the doping anion, determination of metals by deposition and stripping, incorporation of neutral compounds in the polymer membrane, and the novel properties of a polymer surface are presented and discussed.

X-ray photoelectron spectroscopic investigations of the chain structure anddoping mechanisms in polyaniline

Abstract: X-ray photoelectron spectroscopy has been used to investigate the atomic species, and their bonding, within the conductive polymer polyaniline (PANi). PANi was grown electrochemically using HCl as the electrolyte ion and all three of PANi's oxidation states were investigated. Measurements of the C 1s, N 1s, O 1s and Cl 2p core levels and the valence band have been made on each of these oxidation states. Bond potential model calculations have been used to aid the analysis of the observed spectra. The main findings of this work show that semi-quinone radical cations are the dominant species in the conductive form, and that these are localized. Furthermore, evidence is given to verify that hydrolysis accounts for the principal polymer electrochemical degradation process, and that ring substitution of the halogen counter ion also occurs. Valence band measurements indicate a 30-40 degrees torsion angle between adjacent rings along the polymer backbone. The results are discussed in terms of previously reported oxidation mechanisms.

Observation of Propagation Speed of Conductive Front in Electrochemical Doping Process of Polypyrrole Films

Abstract: According to the propagation theory of a conductive zone for the electrochemical doping process of conducting polymer films, an oxidized conductive zone works as an electrode for oxidizing the reduced non-conductive region and is propagated throughout the film under charge transfer control. This theory was verified for polypyrrole films by tracing the temporal and spatial variations of conductive regions in a film. An exhaustively reduced polypyrrole film was laid on an insulating glass plate and connected electrically to an ITO electrode at the marginal part. The film absorbance to a monochromatic light beam was monitored with a photodiode array detector at 14 segments of the film. When the potential of the ITO electrode was stepped to an oxidation potential of the film, an electrochemically oxidized conductive zone was propagated through the film with a manifest phase boundary. The distance from the edge of the ITO electrode to the front of the conductive zone increased linearly with time. The logarithm...

New method for the preparation of thick conducting polymer composites

Abstract: A highly porous and absorbable crosslinked polystyrene, prepared by the concentrated emulsion polymerization method, was used as host polymer for the preparation of conducting, large objects, polymer composites. The composites, whose conductivity can be as high as 0.80 S/cm, were prepared by (i) imbibing the host polymer with a pyrrole (or oxidant) solution, (ii) partially drying the imbibed host polymer, and (iii) imbibing again with an oxidant (or pyrrole) solution for polymerization to take place. The electrical conductivity of the composite and the penetration of polypyrrole in the host polymer are influenced by the polymerization conditions (i.e., the concentrations of oxidant and pyrrole and the nature of the solvents used for the oxidant and pyrrole), the order in which the two imbibing solutions are introduced, and the drying time used after the first imbibation. The mechanical properties of the host polymer are improved with the incorporation of polypyrrole. Scanning electron micrographs of the composites indicate that the polypyrrole coats uniformly as a film the inside of the porous host polymer.