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Molecular Structure and Conductivity of Molecular Conductive Polymer PEDOT (126213-50-1), Polypyrrole, Polyaniline

2014-08-08 来源:亚科官网
Conductive polymers refer to a class of macromolecular materials with conjugated long chain structure. At present, the research field of conductive polymers with good environmental stability, such as polyaniline, polypyrrole and polythiophene, has gradually been formed. Although these materials have better conductivity than eigenconductors, they belong to the insulator or quasi-semiconducting system. The transition of the conducting polymer from the insulating state to the conducting state requires the migration of electrons from the molecular chain, this process of electron transfer is called "doping". The doping and dedoping of the conductive polymer are equivalent to electrochemical oxidation or reduction, so the doping means can be chemical as well as electrochemical. The molecular chain of conductive polymer bring the charge after doping, in order to maintain the material's electrical neutrality, it often need ion with opposite charge to be pairing, which is called the pair ion .
A large number of experimental facts accumulated in the study of conducting polymers concluded that the necessary conditions for the molecular structure of the conducting polymer should be that the long molecular chain has a large π-conjugated system, there is some degree of charge transfer between the repeat units of each chain and the counterion (also referred to as dopant) added to the material.
As same with metal conduction, which requires both free electrons and orbit for electrons motion, polymer conduction also requires charge carriers and orbits that permit free movement of the charge carriers. However, most of the polymers do not have a charge carrier. The charge carrier for the conductive polymer is provided by a "doping" process while the conjugated structure in the long chain of conductive polymers provides track for the free movement of these charge carriers. With regard to the conductive mechanism of the post-doped conductive polymer, the current more mature point of view are show in the following figure.