Electroconductive polymers insulator

CHEMFET devices or chemically sensitive field-effect transistors are potentiometric devices in which the metal layer of a solid-state insulated gate field-effect transistor (IGFET) f29] is replaced with a chemically sensitive electroconductive polymer membrane film. Changes in polymer membrane potential modulate the drain impedance of the space-charge region beneath the insulator. The result is a change in drain current /o under a fixed drain voltage Vd- The potential of the membrane may be modulated in the standard way (as in po-tentiometry, above) or may be modulated by an inert electrode placed beneath the film (but isolated from both the source and drain electrodes) and connected to an efficient electrode for the candidate analyte [30]. 

Redox switches are threshold sensor devices in which the electroconductive polymer is rendered conducting (turned on) under one set of conditions and insulating (turned off) under another. The sharp and rapid change in electrical conductivity through a well-defined resistance transition is essential to the performance of a redox switch. More aptly described as electronic devices, redox switches may be rendered chemically or biologically specific and may be used as simple on/off chemical indicator devices. 

Electroconductivity a is one of the most important characteristics of foams. For solid foams it determines the reliabflity of a foam as an electrical insulator, for liquid foams it serves as a technological parameter which is used to monitor foaming and hardening kinetics of gas-filled polymers. 

Since the electroconductivity of pure water is by several orders of m itude hi er than those of polymers, even smaU amounts of moisture markedly reduce electrical insulation properties of foams. For this reason, measuren nt of dielectric properties is a precise, rapid and non-destructive method of monitoring the kinetics and level of moisture absorption. Thus, the establishment of correlations between dielectric properties and the hygroscopicity of plastic foams makes it possible to solve two practical problems how moisture affects dielectric properties and how to determine non-electrical properties by electrical measurements ... 

As shown in eq. (15.31), ethynylferrocene polymerizes similar to vinylferrocene with various kinds of initiators, and most of the polymers are insoluble. As the polymer has an all conjugated structure, electroconductivity is expected. But actually the electroconductivity is almost the same as an insulator however, it is partially oxidized with iodine or dichlorodicyanoquinone and when Fe(III) is 40-60%, the electroconductivity is 10 -10 Q cm [89,92]. 

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