Karl F. Schoch

Conducting polymers

The fabrication of conducting polymers is briefly described. Advances in stability and processing characteristics, which have been the main barriers to the commercialization of these materials, are examined. The first commercial use of a conducting polymer in a 3 V, coin-sized primary battery is discussed. These batteries are compared with those produced using other technologies, and their possible applications are considered. Potential uses in electromagnetic interference (EMI) shielding, coatings, semiconductor devices, solar cells, and aircraft are discussed.<<ETX>>

Preparation and properties of plasma-polymerized thiophene (PPT) conducting films

Abstract This paper presents, for the first time, conducting films of polythiophene prepared by plasma-polymerization. In this technique, ionized argon is the initiating species for the polymerization of thiophene in a region away from the high RF flux-density. These films displayed a conductivity of 1.8 × 10 −4 S cm −1 after doping with iodine. The surface morphology of the films deposited away from the high RF flux-density region showed topology similar to the films prepared by electrochemical methods. The films deposited near the high RF flux-density region showed a platelet structure.

Deposition and characterization of conducting polymer thin films on insulating substrates

Abstract Chemical polymerization of aniline and pyrrole in dilute aqueous solution was used to produce coatings having a conductivity as high as 0.72 and 0.073 S/cm for films having optical absorbance of 0.032 (800 nm) and 0.012 (1000 nm), respectively. Assessment of the stability of the conductivity for films having optical properties of the coatings during weathering, salt fog and humidity exposure showed that there was some loss in conductivity over an eight-day period, but no deterioration in optical transparency. Electron spectroscopy for chemical analysis was used to determine changes in surface composition and bonding during the environmental exposure tests.

IR response of phthalocyanine thin films to nitrogen dioxide

Abstract The IR-transmission of nickel and lead phthalocyanine thin films decreases dramatically after exposure to NO 2 at room temperature. This effect is caused by the creation of charge carriers and is concurrent with increased electrical conductivity of the films. Both effects can be reversed by heating the films to 160 °C in vacuum. At gas concentrations below approximately 1800 ppm, the absorbance is directly proportional to gas concentration. The detection limit based on IR absorption is approximately 100 ppm compared with a limit of 10 ppb by electrical measurement.

Electrical and optical response of phthalocyanine thin films to No2

Abstract Thin films of several metal phthalocyanine compounds (MPc; M=H 2 , Cu, Ni, Pb,) have been prepared by evaporation onto heated substrates and by plasma deposition on substrates at room temperature. Their electrical and infrared response to NO 2 /air mixtures have been determined at room temperature and at elevated temperatures. Films prepared by evaporation are very sensitive and fast responding at room temperature to low concentrations (25 ppb). While not as sensitive, the plasma deposited films are more mechanically durable. The basis for selectivity of gas detection via an array of sensors is shown. Morphology of the films has been determined by TEM.

Ion-induced conductivity in poly (phenylene sulfide)

New data on the production of electrical conductivity in poly(phenylene sulfide), PPS, by ion irradiation are presented. These and previously reported PPS data are investigated in the framework of a theoretical semiempirical model that relates observed conductivity to parameters associated with the deposition of energy in the polymer by the bombarding ions. It is shown that the onset of conductivity with increasing ion dose is dependent on overlap of individual ion damage regions. A straight line relationship is obtained between log of the ion stopping power and log of the effective overlap radius of the ion damage regions. Furthermore, the magnitude of the values of effective overlap radii are consistent with physical observations and theoretical predictions. At higher ion doses, the rapid increase in conductivity appears to be consistent with a multistage reaction mechanism for the production of conducting species in the polymer. A universal curve of conductivity as a function of dose above threshold dose is seen to fit all of the PPS data up to a dose of a factor of 50 above threshold. This curve and the predictable behavior of the threshold dose allow the selection of ion/dose combinations to produce a desired conductivity.

Comparison of cure conditions for rigid rod epoxy and bisphenol A epoxy using thermomechanical analysis

Thermomechanical analysis was used to compare cure conditions of a bisphenol A epoxy resin composition and the same composition prepared with a rigid rod biphenol epoxy resin. The rigid rod system exhibited a lower curing rate and lower thermal expansion than did the bisphenol A system. The glass transition and thermal expansion of the rigid rod system can be varied by manipulation of the ratio of curing agent to epoxy.

Electroluminescent edge emission from poly (phenylene vinylene) films

Edge emission has been demonstrated from an ITO/poly(phenylene vinylene)/InMg electroluminescent device. Room temperature emission saturated at 0.6 mA mm−2, 14 V, and 9.6 cd m−2 approximately 35 times brighter than face emission from the same device.

Electrical properties of plasma polymerized thin films deposited at high substrate temperature

The authors successfully prepared thin dielectric films containing silicon nitride-type linkages by plasma polymerization of tetramethylsilane in the presence of ammonia. The content of silicon nitride-type inorganic linkage in the polymer film increased with an increase in the substrate temperature from 25 degrees C to 200 degrees C. The rate of deposition of film decreased with an increase in substrate temperature. The dielectric constant and dissipation factor decreased with an increase in frequency. The loss tangent and dielectric constant decreased with an increase in the film deposition temperature from 25 degrees C to 200 degrees C at all the frequencies with an exception at the highest frequency. This has been attributed to the higher silicon nitride content in the films deposited at higher temperatures. A gradual increase in dielectric constant and loss tangent was observed for the films with an increase in measurement temperature. Aging of the plasma deposited films, both in air and oil, improved the dielectric properties. The DC resistivity increased with an increase in film deposition temperature. From these results it is concluded that, in general, the dielectric properties of plasma polymerized films can be improved by increasing the deposition temperature from ambient (which is commonly used) to 200 degrees C.<<ETX>>