Electrical conductors, conjugated polymeric

It has been mentioned already that polypyrrole (25) and polythiophene (26) play an important role as electrical conductors and polymeric anodes in battery cells [2,47,226]. Since the charging and discharging of the conjugated polymer is accompanied by the incorporation and removal of counterions it is clear that the material can also act as a carrier of chemically different anions which influence the physical, chemical and physiological properties of the material [292]. With regard to the full structural elucidation of the polymers it must be added, however, that the electropolymerization process of pyrrole and thiophene does not provide a clean coupling of the heterocycles in the 2,5-positions. Instead, the 3- and 4-position can also be involved giving rise to further fusion processes under formation of complex polycyclic structures [47]. 

Polymeric (isocyanide)gold(i) aryls ( gold oligo-phenylene-ethynylene-isonitriles ) were tested as electrical conductors at metal-molecule-metal junctions (7r-conjugated molecular wires), but the preparation, structure, and properties of the materials were not fully disclosed (Scheme 52).218... 

Even if unwanted chemical transformations of doped conjugated materials can be avoided by strict exclusion of air, the long-term stability is limited by a de-mixing of dopant and redox system. An alternative approach to persistent electrical conductors is therefore concerned with the synthesis of intrinsic conductors. Toward that end the lowering of the band gap is desirable which, on the other hand, is known to reduce the chemical stability. The synthetic approaches taken must therefore focus on a compromise between electronically attractive 7i-structure, stability and processability of the material. In conclusion, it is the flexible combination of different areas of research which provides new insights into the properties of monomeric, oligomeric and polymeric radical ions. 

The chemistry of polymers gives, as must by now be apparent, wide scope for developing materials with new and useful properties. In electrics they now do far more than just insulate cables. Polymeric conductors, which have already been in use for some years, are among the most remarkable. Chains with conjugated backbones— those with alternating single and double bonds, in which the electron doud extends over the whole... 

One active area of research is completely missing. These are the optical and electrical properties, with effects such as the high conductivity of doped conjugated polymers, electro-luminescence in polymeric light emitting diodes, or the ferro- and piezoelectricity of poly(vinylidene fluoride), to cite only a few examples. There is no good reason for this omission, only that I did not want to overload the book with another topic of different character which, besides, mostly employs concepts which are known from the physics of semi-conductors and low molar mass molecules. 

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