Showing papers on "Conductive polymer published in 1983"

The chemical and physical properties of pyrrole‐based conducting polymers: The oxidation of neutral polypyrrole

Abstract: A series of experiments on the physics and chemistry of polymers derived from pyrroles show that the oxidation of neutral insulating polypyrrole (PP0) to its conducting counterpart (PP+) is a multistep process. In particular, the conductivity of the polymers increases only in the early stages of oxidation, whereas significant changes in the optical and EPR properties occur in later stages of the oxidation when no further changes in the conductivity take place. The early stages of oxidation lead to an ionic (PP+ anion−) polymer and the later stages of oxidation result in chemistry at the nitrogen atoms of the pyrrole rings. Similar behavior is observed for all the oxidized pyrrole polymers independent of the method of oxidation.

Electrochemical synthesis of electrically conducting polymers from aromatic compounds

Abstract: Amorphous, electrically conducting polymeric films can be deposited from acetonitrile solutions of specific aromatic compounds containing an appropriate electrolyte. Free-standing films peeled off a platinum electrode have electrical conductivities between 10-3 and 1 Ω-1 -cm-1. Polymers resembling the better-known polypyrrole have been obtained from benzenoid, nonbenzenoid, and heterocyclic monomers. A few characteristic examples are discussed to highlight the characterization efforts. Also discussed are the chemical investigations which have provided some insight into the mechanism of formation and the structure of these conducting polymers.

Conductive polymers

Abstract: There has been considerable interest among chemists and physicists during the past ten years in electrically conductive organic compounds [1]. The possibility of conductive materials that are light weight, inexpensive and easily processed has been especially attractive. This paper will describe what makes these organic materials conductive, and their properties in general, as well as results of recent work.

Stability of Conducting Polythiophene and Derivatives

Abstract: The doped PMeT (poly-3-methylthiophene) reveals that storage in air affects neither the CF3SO3(-) doping level nor the conductivity. These results are supported by the infrared analysis. This conducting polymer is characterized by a large broad band in the near infrared due to free carriers and by absorption patterns associated with the dopant CF3SO3(-). The undoped PMeT is found to behave in the same fashion. PT (polythiophene) and P(Me)2T show the same interesting stability characteristics, in contrast to the experimental precautions that must be taken with other types of organic conducting polymers. These materials have great thermal stability: 200-250 C in air and 700-800 C in an inert atmosphere or vacuum. They are stable in concentrated acidic media but are slowly attacked in basic solutions. Also investigated is the stability under electrochemical treatment.

Electronic properties of sulfur containing conjugated polymers

Abstract: Valence effective Hamiltonian (VEH) calculations are performed on a number of sulfur containing organic conjugated polymers of interest to the conducting polymers area. Theoretical results for parameters related to conductivity such as ionization potentials, bandwidths, and bandgaps are presented. Systems considered include various derivatives of poly (p‐phenylene sulfide), polybenzothiophene, and polythiophene, as well as potentially interesting compounds such as polythieno [3,2‐b] thiophene and polyvinylene sulfide. The electronic structure description afforded by the VEH method for sulfur containing polymers is demonstrated to be of the same quality as that presented previously for hydrocarbon polymers. In particular, for ionization potentials, good agreement with available experimental data on poly (p‐phenylene sulfide) and polybenzothiophene is obtained, after scaling downward the VEH values by a 1.9 eV polarization correction. The comparison between the theoretical and experimental XPS spectra for polybenzothiophene is excellent with use of the same energy scaling factor previously employed for polyacetylene, poly(p‐phenylene), and poly(p‐phenylene sulfide). These results, in conjuction with previous results obtained on hydrocarbon polymers, lend confidence in the predictive capabilities of this purely theoretical technique. Calculations show that polyvinylene sulfide, as yet unsynthesized, should display very promising characteristics as a conducting polymer.

Valence effective Hamiltonian technique for nitrogen containing polymers: Electronic structure of polypyrrole, pyrolized polyacrylonitrile, paracyanogen, polymethineimine, and derivatives

Abstract: We present the parametrization of nitrogen for use in the valence effective Hamiltonian (VEH) technique. We describe five different parametrization schemes and discuss the quality of the results each of them affords. The VEH method is then applied to the study of the electronic structure of nitrogen containing polymers of interest with regard to the conducting polymers area. These polymers include polypyrrole, poly‐β‐dimethylpyrrole, poly‐N‐methylpyrrole, pyrolized polyacrylonitrile, paracyanogen (polypyrazinopyrazine), and polymethineimine [CH=N]x. Parameters related to the conductivity properties upon doping such as ionization potentials, bandgaps, and bandwidths, are discussed in detail.

Organic conductive films for semiconductor electrodes

Abstract: According to the present invention, improved electrodes overcoated with conductive polymer films and preselected catalysts are provided. The electrodes typically comprise an inorganic semiconductor overcoated with a charge conductive polymer film comprising a charge conductive polymer in or on which is a catalyst or charge-relaying agent.

PTC compositions and devices comprising them

Abstract: Novel conductive polymer compositions which exhibit useful PTC behavior are produced by cross-linking processes. By correlating the polymer, the conductive filler dispersed therein, and the cross-linking conditions, PTC compositions having desired resistance/temperature characteristics can be prepared. In particular the cross-linking can be carried out so as to provide compositions having a switching temperature around the cross-linking temperature. The invention is applicable to both elastomeric and thermoplastic polymers, and provides for the first time a method of making PTC compositions exhibiting useful PTC behavior from elastomers.

Proposal of Electro-Optical Switching and Memory Devices Utilizing Doping and Undoping Processes of Conducting Polymers

Abstract: New optical switching and memory elements utilizing the spectral change of conducting polymers by electro-chemical doping and undoping are proposed.

Characteristics of Electro-Optic Device Using Conducting Polymers, Polythiophene and Polypyrrole Films

Abstract: Detailed characteristics of electro-optic elements (color switching and memory) utilizing the spectral change of conducting polymers by electrochemical doping and undoping are studied. The response time of color switching, for example, red↔blue in polythiophene film in the electrolyte of LiBF4/acetonitrile is 30~100 msec under the applied voltages of -2.0↔+4.0 V vs. Li plate. More than 103 cycles of color switch are observed quite reproducibly. Three color states of yellow green, dark brown and blue are demonstrated for polypyrrole film.

Poly(1,6-heptadiyne), a free-standing polymer film dopable to high electrical conductivity

Abstract: Polymerization of 1,6-heptadiyne on the surfaces of concentrated solutions of homogeneous Ziegler-Natta catalysts leads to insoluble, free-standing films with metallic luster. “Doping” of these films by treatment with acceptors results in conductivities up to 1 S/cm. The polymer has been characterized in terms of its molecular structure, its solid-state structure and physical properties, the nature of the doping process, and its thermal and oxidative stability. Poly( 1,6-heptadiyne) provides a number of contrasts to polyacetylene in its molecular and solid-state structure which yield some information about the requirements for conductive polymers. Electrically conductive polymers have been the subject of sporadic interest for at least the last 25 The discovery of a method of preparation of free-standing films of polyacetylene4 sparked a rebirth of interest in this conjugated polyene that had been previously studied in powder form.s The films were more amenable to study of physical properties and for many potential applications. A number of dopants were subsequently found to be effective for raising the conductivity into the metallic regime.6 At the inception of the present study, no other substituted polyenes had been formed as films in situ during polymerization. Our initial goal was to determine whether other conjugated polyenes could first be polymerized in situ to free-standing films and then doped to high electrical conductivity. If this goal could be reached, optimization of properties such as flexibility, ductility, thermal transitions, oxidative stability, etc. might be achieved by modification of substituents on the polyene chain. It was known,’ however, and subsequently confirmed by using the Shirakawa catalyst* that substituted acetylenes, e.g., methyl and ethyl derivatives, polymerize sluggishly in comparison to acetylene itself. Because cyclopolymerization was of such utility in the synthesis of substituted olefin derived polymer^,^ it was our belief that cyclopolymerization of diacetylenes might prove useful in the preparation of substituted polyacetylenes. The polymerization of 1,6-heptadiyne (1) using an insoluble

Polypyrrole‐semiconductor Schottky barriers

Abstract: Junctions between polypyrrole, a conducting polymer formed by electrooxidation, and n‐type semiconductors have been studied. Cadmium sulphide and titanium dioxide were chosen as substrates as a complement to earlier studies on silicon. The junctions behave as Schottky barriers on these semiconductors. The series resistance of the polypyrrole film is large and was taken into account in the evaluation of the data. The barrier heights of the junctions are compared with those found with ordinary metals. It is deduced that the work function of polypyrrole must be close to 5 eV.

Magic angle spinning NMR of conducting polymers

Abstract: Because of their typically intractable nature, conducting polymers as a class of materials have proved particularly difficult to characterize by the conventional techniques of polymer analysis. We present here examples of the application of a powerful new tool, cross-polarization magic angle spinning (CMPAS) 13C NMR spectroscopy, to the investigation of the structure and reactions of the conducting polymers polyacetylene and polypyrrole.

Chemical anchoring of organic conducting polymers to semiconducting surfaces

Abstract: According to the present invention, an improved method of coating electrodes with conductive polymer films and/or preselected catalysts is provided. The charge-conductive polymer is covalently or coordinatively attached to the electrode surface to strengthen the adhesion characteristics of the polymer to the electrode surface or to improve charge-conductive properties between the conductive polymer and the electrode surface. Covalent or coordinative attachment is achieved by a number of alternative methods including covalently or coordinatively attaching the desired monomer to the electrode by means of a suitable coupling reagent and, thereafter, electrochemically polymerizing the monomer in situ.

Polypyrrole: An Electrochemical Approach to Conducting Polymers

Abstract: Until recent times, almost all of the known organic polymers were essentially electrically insulating, with room-temperature conductivities of 10−10 ohm−1 cm−1 or less. The desirability of having low-density, flexible, processible conductors provided the impetus for finding ways of enhancing the electronic conductivity of polymers. The electrical and optical properties of these materials depend on the electronic structure and basically on the chemical nature of the repeating unit. The general requirements of the electronic structure in these polymers were recognized and described many years ago.1 The electronic conductivity is proportional to both the density and the drift mobility of the carriers. The carrier drift mobility is defined as the ratio of the drift velocity to the electric field and reflects the ease with which carriers are propagated. Enhancing the electrical conductivity of polymers then requires an increase in the carrier mobility and the density of charge carriers. The particular importance of the delocalized π-electrons to form energy bands of high-mobility carriers was stressed early on2 and a large number of polymers were considered as having this characteristic.3 These same considerations have been discussed from a somewhat broader perspective that include polymeric charge-transfer complexes and organometallics.4 The dramatic conductivity enhancements reported recently5 in polyacetylene when treated with strong oxidants have spurred a resurgence of interest in these systems including several articles reviewing the electronic structure of these polymers.6–8

Organic metals. Introduction of indium and thallium tetrachloride anions into polyacetylene by anodic oxidation

Abstract: Polyacetylene films can by oxidized electrochemically in LiCI–MCI3–nitromethane solutions (where M In and Tl) to give highly conducting polymers.

Electrolytic capacitor with polymer conductor

Abstract: A solid electrolytic capacitor includes a conductive polymer electrolyte. The electrolyte may comprise p-doped polyacrylonitrile, polypyrrole, or polyacetylene.

Conductive polymers exhibiting ptc characteristics

Abstract: Conductive polymer compositions which exhibit PTC behavior and comprise carbon black (or other particulate conductive filler) dispersed in a cross-linked polymer component comprising a cycloolefin polymer having a crystallinity of at least 5% and a melting point in the range 0° to 80° C. These compositions are particularly useful in the form of heaters which self regulate at a temperature in the range of 0° to 70° C. Such heaters are particularly useful for freeze protection and for heating human and other animal bodies.

Electrically conductive polymer composition

Abstract: Electrically conductive polymers, especially polypy- . rroles, are formed with a charged polymeric dopant suplying the necessary counter -ions to stabilise the charged conductive form of the conductive polymer. The physical properties of the conductive polymer can thus be usefully modified in ways different from those achieved by non-polymeric dopants or by forming the conductive polymers in pre- existing bodies of non dopant (i.e. uncharged) polymers.

Electro conductive polymer compositions and new materials found useful in their preparation

Abstract: Preparation of new, useful and novel highly electro-conductive polymer compositions via the dispersion of electrically particulates in conjunction with small proportions of certain organo aluminates, titanates and/or zirconates in polymeric substrates is hereinafter described. Further the production of heretofore unknown classes of organo aluminates, titanates and zirconates useful in the practice of this invention is disclosed and generically useful subclasses of these compounds defined. Advantages other than improved electrical conductivity of the resultant composites, i.e., process and physical property improvements are also documented for compositions containing said additives and particulate materials and/or composites in polymeric dispersions, and/or compositions of said particulates with said organic aluminates, titanates and zirconates.

Stable electrically conducting polymers and method of making

Abstract: An electrically conducting polymer is disclosed which includes poly(N-alkyl 3',3 carbazolyl) at least a portion of which is doped with a compatible charge transfer acceptor to provide p-type electrical conductivity, and in which the alkyl group is one selected from the group consisting of ethyl and methyl or a combination thereof.

Poly (2,2' - bithiophene) : an electrochromic conducting polymer

Abstract: We present the optical properties of poly (2,2' bithiophene) and show that this material exhibits electrochromic behavior.

Conductive polymer composition

Abstract: Electrical conductivity of a polymeric material such as poly(phenylene sulfide) is enhanced by exposure to iodine vapor in the presence, optionally, of aluminum

Conditions for Reticulated Crystalline Doping of Polymer with Charge Transfer Complexes

Abstract: Crystallization of the conductive charge transfer (CT) complex forming a reticulated, dendritic morphology within a polymeric matrix during film casting is a new way for obtaining conductive polymers. Subject to proper crystallization conditions during film casting one can obtain materials with high conductivity at a concentration of additives as low as 1 wt%. This paper describes a model concept allowing for the selection of proper crystallization conditions leading to suitable morphology of crystalline additives. It is based on an analysis of morphologies from evaporating solutions containing polymer and low molecular weight CT complexes-forming additives. Considerations are based on the results obtained for TTF–TCNQ CT complexes crystallized in polycarbonate and polystyrene matrices.