Electronic Structure and Relation to Properties

The relationship between chemical structure and electronic properties in conjugated-chain polymers has been extensively reviewed409 . In this section we only briefly discuss the issues which seem relevant from the point of view of polymer science. 

In principle, it should be possible to design and synthesise a polymer with a sufficiently small band gap that it would be conducting without doping. Bredas 4I1) has discussed theoretical calculations of the band-gap of polymers based on polyisothianaphthene. A number of polymers have band-gaps predicted to be less than 1 eV, with polyisonaphthothiophene having a predicted band-gap of almost zero. Jenekhe412 has made polymers with a band-gap of 0.73 eV, based on polythiophene with alternating aromatic and quinonoid units (Fig. 12). 

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