Showing papers on "Conductive polymer published in 1989"

Polyanilines: a novel class of conducting polymers

Abstract: The polyanilines are a class of polymers the base form of which has the general formula [graphic omitted] containing y reduced and (1 –y) oxidized repeat groups. y can in principle be varied continuously from one, the completely reduced material, to zero to give the completely oxidized polymer. The emeraldine oxidation state (y= 0.5) consists of alternating reduced and oxidized groups. It can be protonated, i.e. doped, by aqueous acids with a concomitant increase in conductivity of almost 10 orders of magnitude (to a maximum conductivity of 101–102 S cm–1), forming a polysemiquinone radical cation such as [graphic omitted] which contains a delocalized half-filled broad polaron energy band. The polymer is readily solution-processed into films and fibres which can be mechanically aligned, the doped forms of which have a conductivity parallel to the direction of alignment significantly greater than that of non-aligned material. X-Ray studies show that the doped and undoped polymer exist in several different crystalline forms. A wide variety of derivatives can be synthesized by substitution on the ring or on the nitrogen.

'Synthetic metals': a novel role for organic polymers

Abstract: Summary form only given. The basic chemistry and physics of polyacetylene, (CH)/sub x/, the prototype conducting polymer which is characteristic of most other conducting polymers, were described together with a description of the polyanilines, a large new class of conducting polymers. Potential technological applications were discussed. Polyacetylene, (CH)/sub x/ is obtained in the form of silvery, flexible films by the polymerization of gaseous acetylene. >

Conductive polymer bronzes. Intercalated polyaniline in V2O5 xerogels

Abstract: La polymerisation vedox de l'audine dans les xerogels le V 2 O 5 ,nH 2 O donne un composite moleculaire contenant la forme protome de la polyaniline; la conductivite electrique et le coefficient le Seebecti du composite diminuent avec la temperature

Electronically conductive polymer fibers with mesoscopic diameters show enhanced electronic conductivities

Abstract: La polymerisation du pyrrole et du methyl-3 thiophene dans les pores d'une membrane Nuclepore donne les membranes composites dont les pores sont remplis par les fibres de polymere conducteur; la conductivite des fibres augmente lorsque leur diametre diminue

Conductive polymers and plastics

Abstract: Compounded conductive plastics - types of conductive fillers, applications plated conductive plastics - types of plated conductive plastics, applications intrinsically conductive polymers (ICPs) - state-of-the-art technology, potential uses, coating applications.

Thermoelectric power and conductivity of heterogeneous conducting polymers

Abstract: We discuss the interpretation of thermoelectric power in heterogeneous media, and using a compilation of many sets of data, we analyze the thermopower of conducting polymers as a function of conductivity and of temperature. For samples of very high conductivity, the thermopower (but not the conductivity) shows typical metallic temperature dependence, which is consistent with a heterogeneous model of metallic fibrils separated by thin electrical barriers. Metallic thermopower is expected rather generally to show significant nonlinearities as a function of temperature, and we demonstrate that the observed thermopower in some highly conducting polymers is very similar to the diffusion thermopower of metals in which a knee is produced at low temperatures by the electron-phonon interaction. The thermopower of moderately doped conducting polymers, like their conductivity, is generally consistent with a significant contribution from variable-range hopping.

Relation between structure and electronic properties of ion irradiated polymers

Abstract: Ion beam irradiation of saturated polymers leads to the formation of new carbonaceous materials exhibiting enhanced electrical conductivity and increase of the optical absorption, which shifts gradually from the near UV to the visible. Different techniques, such as the analysis of the gas evolved from the polymer during irradiation, RBS and ERDA show the loss of the more volatile elements which results from the dissociation of the molecular structure. The consideration of different types of polymers indicates that some specific structural elements are preserved and that unsaturated bonds appear at high fluences, which are responsible for the loss of the insulating properties of polymers. The chemical bond modifications are discussed in view of infrared spectroscopy and ESCA, which shows the formation of graphite-like phases in polyimide and explains the high level of conductivity reached in this type of polymers. The appearance of conducting properties cannot be described by a simple model of carbonization and are governed both by the molecular structure of the parent polymer and the beam conditions. The behaviour of polyimide will be considered more in details because of the remarkable level of conductivity ( σ = 10 3 S/cm) and heat stability reached upon irradiation with heavy ions, which render this type of surface processing very efficient in order to produce conductive polymers.

Spectroscopic and electrochemical studies of charge transfer in modified electrodes

Abstract: Experimental results from electrochemical e.s.r. on electrodes modified with conducting polymers such as polyaniline, polypyrrole and polythiophene are presented. The results show that the polymer exists in two forms, one stable when it is insulating (α) and the other (β) when it is conducting. In the conducting region the kinetics of the transformation of the metastable α form into the β form can be followed by e.s.r. It is further shown that in the lightly oxidised films there is a one-to-one correlation between charge injected and e.s.r. spins. These results are explained by a chemical redox model as opposed to a delocalised band.Results from a.c. impedance studies are presented. These results are explained by an equivalent circuit which includes a novel transmission line with differential resistances. Theoretical impedance plots are derived. Experimental results show that the polymer resistance and the resistance of the aqueous pores are equal. Reasons for this finding are discussed.

Fusible Conducting Poly(9-alkylfluorene) and Poly(9,9-dialkylfluorene) and Their Characteristics

Abstract: Conducting poly(9-alkylfluorene) and poly(9,9-dialkylfluorene) with long alkyl chains have been prepared and found to be fusible at relatively low temperature. Unlike in poly(3-alkylthiophene), electrical conductivity and band gap energy do not change remarkably at the solid-liquid phase transition. These polymers also demonstrate drastic changes of optical and electrical properties upon doping.

Functionalized Conducting Polymers—Towards Intelligent Materials

Abstract: Organic conjugated polymers and oligomers constitute a three-dimensional network of molecular wires, in which all monomeric units can be functionalized with various prosthetic groups. By varying the nature of these groups, specific interactions with external physical or chemical phenomena can be developed in these materials, leading to molecular devices such as sensors, transducers, memories and logic operators. Chemists have already mastered the realization of many of these functional elements, which mimic those existing in organized beings.The further assembly of these elements in multifunctionalized organic conducting polymers and oligomers will represent the next step towards intelligent materials.

Electrically conductive polymeric

Abstract: Structures containing conducting polymers and methods of fabrication thereof. Electrical conductivity can be induced in polymers selected from the group of substituted and unsubstituted polyanilines, polyparaphenylenvinyles, substituted and unsubstituted polythiophenes substituted and unsubstituted poly-p-phenylene sulfides, substituted polyfuranes, substituted polypyrroles, substituted polyselenophene, polyacetylines formed from soluble precursors, combinations thereof and blends thereof with other polymers. The polymer contains a doping precursor, selected from the group of onium salts, iodonium salts, triflate salts, borate salts and tosylate salts and sulfonoxylimides. Conductivity can be selectively induced in the polymer by selectively doping upon selective exposure to a source of energy such as electromagnetic radiation, an electron beam and heat. The electrically conductive polymers of the present invention are useful as electron discharge layers for electron beam applications, such as, SEM observations, as electromagnetic interference coatings on dielectric surfaces and as electron beam resist which acts as a discharge layer.

Memory effects in conducting polymers.

Abstract: The kinetics of electrochemical doping of polyaniline films has been studied using in situ ESR experiments. It has been found that the kinetics and the doping level achieved during a potential-reading step depend on the previous electrochemical events undergone by the sample. It is shown that slow relaxation process takes place in the polymer film while it is maintained in the neutral state. Possible relations to hysteresis effects are discussed.

Electrochemistry of Conductive Polymers: VI . Degradation Reaction Kinetics of Polyaniline Studied by Rotating Ring‐Disk Electrode Techniques

Abstract: The degradation reaction kinetics of oxidized polyaniline has been studied employing rotating ring-disk electrode techniques. Polyaniline films were grown on the disk electrode and were then oxidized at a potential more positive than 0.90V vs. Ag/AgC1, while the degradation product (benzoquinone) was monitored at the ring electrode at an applied potential of 0.05V. The product was monitored either with the disk potential maintained at >0.90V (closed-circuit experiment) or with the disk circuit disconnected after the polyaniline film was oxidized for some time (open-circuit experiment). The results of closed-circuit experiments indicate that electrochemical generation of oxidized polyaniline was a limiting step and its rate decayed for a given amount of polyaniline film according to the zeroth order. The rate of hydrolysis for the oxidized polyaniline in quinonoid forms was determined to be consecutive first order from open-circuit experiments. The dependencies of the hydrolysis reaction on the acidity of the degradation medium and sulfate concentrations have also been studied; the results are consistent with the Schiff base hydrolysis mechanism.

Electrochemical investigations of electronically conductive polymers. 2. Evaluation of charge-transport rates in polypyrrole using an alternating current impedance method

Abstract: An ac impedance method was used to determine apparent diffusion coefficients associated with the oxidation of polypyrrole. This method was applied to the reduced (nonconductive) form of the polymer, and the polymer remained in the nonconductive state throughout the duration of the experiment. Apparent diffusion coefficients obtained were similar in magnitude to coefficients obtained by a related current-pulse method. Diffusion coefficients obtained from finite diffusion data were ca. a factor of 3.4 times larger than coefficients obtained from semiinfinite diffusion data.

Permanently doped polyaniline and method thereof

Abstract: The present invention relates to an electrically conducting polymer, the water-insoluble polymer having essentially permanent self-doping properties, and the polynmer comprises: (a) electrically polymerized polyaniline in covalent combination with (b) an organic dopant having at least one sulfonic acid functional group. The electrically conducting polymer-dopant is preferred wherein the organic dopant is selected from benzenesulfonic acid, toluenesulfonic acid, benzenesulfonyl chloride, dodecylbenzenesulfonic acid, poly(vinylsulfonic) acid, trifluoromethanesulfonic acid, 1-butanesulfonic acid, modified NAFION, 2,3,5-trichlorobenzenesulfonic acid, vinylphenylsulfonic acid, or the alkali metal salts thereof. In another aspect, the present invention discloses a method to produce a water-insoluble polyaniline in which an aromatic organic dopant is covalently bonded to the polyaniline, which method comprises (a) electropolymerizing aniline in an aqueous solvent which contains the organic dopant. These permanently doped polyanilines are useful as films for electric battery electrodes, and for electrochromic applications.

Charge transport in conducting polymers

Abstract: Experimental data on the electrical conductivity of conducting polymers is reviewed. Polyacetylene is regarded as a prototype and the conductivity is studied as a function of doping level, temperature, frequency and conjugation length. The consistency of the data with a model of anisotropic variable range hopping is pointed out, with the exception of very highly doped samples, where in addition to hopping also temperature-independent tunnelling between large conducting domains has to be assumed.