Effects of bridging groups on electronic structures of conjugated cyclic polymers

Theoretical investigation was performed to elucidate effects of the bridging groups (X) on the bandgaps of conjugated cyclic polymers. In addition to heterocyclic polymers such as polythiophene, polypyrrole and polyfuran, the polymers concerned in this study include the conjugated cyclic polymers which contain bridging groups of YZ2 forms (CH2, CF2, SiH2 and SiF2) or YZ forms (CCH2, CO and CS). Geometrical structures of the polymers were optimized through semiempirical band calculations with AM1 Hamiltonian. A modified extended Hückel method was employed to obtain electronic properties of the polymers. Effects of the bridging groups on bandgaps of the polymers were analyzed in terms of geometrical relaxations and electronic perturbations.