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Preparation and Electrical Properties of Conducting Polyaniline-Polycarbonate Composite Films

Conducting polymer polyaniline and insulating polymer polycarbonate composites have been prepared. Electrical conductivity can be controlled in a wide range (more than 15 orders of magnitude) by a small amount of polyaniline. This characteristic can be explained by a percolation model. That is, at the threshold concentration, the electrodes must be bridged by a conducting channel of polyaniline. The percolation threshold and critical exponent of the conductivity parallel to the film surface are different from those perpendicular to the film surface. This suggests the anisotropy of conductivity in the composite. The conductivity of a high polyaniline concentration composite is found to be stable up to 160° C.

Electrooptic Bistability of a Ferroelectric Liquid Crystal Device Prepared Using Charge-Transfer Complex-Doped Polyimide-Orientation Films

Enhancement of bistability and response speed in a surface stabilized ferroelectric liquid crystal (SSFLC) electrooptic device was realized by doping polyimide-orientation films with a charge-transfer complex (CTC) and performing appropriate rubbing. The effects of the enhancement are thought to be attributable to the appropriate AC conductivity of CTC-doped polyimide films which are capable of neutralizing accumulated surface charges brought about by electrical polarization contributing to the spontaneous polarization of the ferroelectric liquid crystal.

Preparation and Electrical Property of Polypyrrole-Polyethylene Composite

Polypyrrole-polyethylene composites have been prepared by pressing the mixture of polypyrrole coated and non-coated polyethylene spheres. Electrical conductivity is enhanced by more than 16 orders of magnitude and its activation energy decreases remarkably at concentration of polypyrrole coated polyethylene above around 10-20%, which corresponds to effective polypyrrole concentration of 0.1-0.2%. These characteristics can be explained by a percolation model. That is, at this concentration electrodes are bridged by conducting channel of doped polypyrrole. Thermoelectric power increases in proportion to absolute temperature and is independent on concentration of polypyrrole coated polyethylene sphere above 30%, which support the percolation model. The electrical property of this polypyrrole-polyethylene composite is found to be stable up to 160°C. The application of this composite to the semiconducting layer of a cable has been proposed.

Characteristics of aluminium solid electrolytic capacitors using a conducting polymer

Abstract In order to form an electrochemically polymerized polypyrrole film on an electrically insulated dielectric layer surface, a conductive precoating layer was first deposited, at the expense of electrical conductivity. Using the precoating layer as the anode, a polypyrrole layer was then deposited electrochemically in preparation for the fabrication of a solid electrolytic capacitor in which the composite conducting polymer layer was used as a solid electrolyte. Soluble polyaniline could be used as a conductive precoating layer as well as polypyrrole formed by chemical oxidizing polymerization. The capacitor using the composite solid electrolyte presented excellent impedance frequency and temperature characteristics; moreover, the solid electrolyte showed ‘self-healing’ and non-polar behaviour.

Solid electrolytic capacitors using an aluminum alloy electrode and conducting polymers

Abstract Solid electrolytic capacitors, in which an aluminum–zirconium (Al–Zr) alloy foil is used as an electrode and a composite conducting polymer layer as a counter-electrode, were prepared and investigated. Soluble polyaniline (PAn) doped with carboxylic acid was used as a conductive precoating layer; using the precoating layer as an anode a polypyrrole layer was formed by electrochemical polymerization to form a composite conducting polymer layer. This method was successfully used in forming the counter-electrode of new alloy electrode capacitors. The capacitors show high capacitance per unit area and excellent high-frequency performance.

Percolation conduction in polymer composites containing polypyrrole coated insulating polymer fiber and conducting polymer

Abstract Electrical conductivity of polymer composite containing insulating polymer fiber coated with thin polypyrrole layer has been found to increase remarkably by more than ten orders of magnitude above some threshold concentration. The activation energy of the electrical conductivity also changes drastically above this threshold. Thermoelectric power at concentration above this threshold is nearly the same with that of doped polypyrrole. The threshold concentration has been found to be dependent on the length of fiber remarkably. Longer length of fiber exhibits lower threshold concentration. These results are discussed in terms of percolation theory by taking the shape of fiber into consideration. Percolation conduction is also observed in other composites made of insulating polymers containing conducting polymers such as polyaniline.

Electrical property of polypyrrole-insulating polymer composite

Abstract PMMA small spheres were coated with polypyrrole by chemical polymerization utilizing FeCl 3 as a catalyst. Polypyrrole-PMMA composite has been prepared by the hot press of the mixture of polypyrrole coated PMMA spheres and non-coated PMMA spheres with appropriate concentration. Polypyrrole-PE composite has also been prepared by a similar method. Electrical conductivity has been controlled in the wide range (10 −17 ∼10 1 S/cm) by changing the concentration of coated spheres in non-coated spheres. That is, when the concentration of PPy coated sphere exceeds 10∼20% remarkable enhancement of conductivity by more than 17 orders of magnitude was observed. The activation energy of conductivity also changed drastically at this concentration. Low thermoelectric power of 6μV/K was evaluated for the composite of coated sphere concentration exceeding 20%. This insulator-metal transition like characteristics can be explained by a percolation model. That is, at this concentration electrodes are considered to be bridged by conducting path (polypyrrole). By taking thickness of polypyrrole layer into consideration the concentration of polypyrrole at the percolation threshold is evaluated to be less than 0.1%.

Electrical Conduction by Percolation Process in Insulating Polymer Containing Small Amount of Conducting Polymer

Electrical conductivity is studied in two component composites, one of which is insulating polymer (nylon6, nylon66) in fibers coated with conducting polypyrrole and the other, polyethylene in spheres without coating. Conductivity is enhanced by more than 15 orders of magnitude when the concentration of polypyrrole-coated insulating polymer exceeds 2?5 vol%, which corresponds to an effective polypyrrole concentration of 0.01?0.03 vol%. This insulator-metal transition-like characteristic can be explained by a percolation model. Thermoelectric power is proportional to absolute temperature and is independent of the concentration of polypyrrole-coated insulating fibers above the percolation threshold, which support the percolation model. The percolation threshold depends on the shape of the coated fibers of the insulating polymer but does not depend on the type of coated insulating polymer. The percolation threshold increases with decreasing length of polypyrrole-coated insulating fibers.

Preparation and characteristics of capacitors with organic conductor as solid electrolyte by ion-assisted evaporation

Ion-beam-assisted deposition of organic materials has been proposed for obtaining high-quality thin films. As an example, organic thin films have been prepared by means of evaporation of 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex on porous oxide Al plates under ion beam irradiation. A Solid electrolytic capacitor with a large capacitance and a good frequency response can be fabricated utilizing thin films obtained with this method as solid electrolyte.

Electrolytic Capacitor Employing Polypyrrole as Solid Electrolyte

Abstract New type of aluminum and tantalum electrolytic capacitors employing polypyrrole as solid electrolytes were developed. The surface of a dielectric is covered with electroconductive pre-coating thin layer of polypyrrole prepared by chemical oxidative polymerization. Then utilizing this layer as an anode, electrochemically polymerized polypyrrole is filled in micropores.