Boxes electrically conductive polymer

Box 15-3 Protein Immunosensing by Ion-Selective Electrodes with Electrically Conductive Polymers... 

What is the purpose of the electrically conductive polymer in the ion-selective electrode in Box 15-3 What is the advantage of replacing the filling solution of a liquid-based ion-selective electrode with a conductive polymer ... 

All metals conduct electricity on account of the mobility of the electrons that bind the atoms together. Ionic, molecular, and network solids are typically electrical insulators or semiconductors (see Sections 3.f3 and 3.14), but there are notable exceptions, such as high-temperature superconductors, which are ionic or ceramic solids (see Box 5.2), and there is currently considerable interest in the electrical conductivity ol some organic polymers (see Box 19.1). 

Because they are molecular compounds, most polymers are electrical insulators. However, polymers that have alternating double bonds along the chain can be used to conduct electricity (Box 19.1). These conducting polymers tend to have long chains with few branches. 

Figure 15.1. Electrical conductivity against price for conventional polymers and polymer composites (40). Boxes representing both published experimental data and calculated upper bounds for CNT - composites were superimposed on the figure.

Most polymers are electrical insulators, but conducting polymers are known (see Box 19.1). 

Conductive polymer composites can be defined as insulating polymer matrices which have been blended with filler particles such as carbon black, metal flakes or powders, or other conductive materials to render them conductive. Although the majority of applications of polymers in the electrical and electronic areas are based on their ability to act as electrical insulators, many cases have arisen more recently when electrical conductivity is required. These applications include the dissipation of electrical charge from rubber and plastic parts and the shielding of plastic boxes from the effects of electromagnetic waves. Consequently, materials scientists have sought to combine the versatility of polymers with the electrical properties of metals. The method currently used to increase the electrical conductivity of plastics is to fill them with conductive additives such as metallic powders, metallic fibres, carbon black and intrinsically conducting polymers such as polypyrrole. 

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