ENERGETICS AND GEOMETRY OF CONDUCTING POLYMERS FROM OLIGOMERS

Reliable estimates concerning the energy difference of the aromatic-benzenoid and quinonoid forms of conducting polymers can be obtained from small cluster calculations if the oligomers are terminated properly, and the energy per repeating unit of the polymer is estimated by the finite difference method. Accordingly, polythiophene and polythiophene and polypyrrole should have an aromatic ground state in agreement with other theoretical and experimental results. Poly(isothianaphthene) and poly(thiathiophene), on the other hand, should have quinonoid ground states.