| abstract |
Polycondensation of, for example, squaric acid with a benzodihydropyrrole, benzodithiazole, neocuproine, terthienyl or an aromatic diamine gives a semiconductive alternating copolymer having a small band gap. It is alternatively possible to use croconic acid or 5,6-dihydroxy-5-cyclohexene-1,2,3,4-tetraon instead of squaric acid. An alternating copolymer of croconic acid and a methyl-substituted benzodithiazole has the following repetititve unit: |