CONFORMATIONS AND ELECTRONIC-STRUCTURES OF POLY(KETENE) AND RELATED CONJUGATED POLYMERS - REDUCTION OF THE N-PI-STAR BAND-GAP

In an effort to design polymers with smaller band gaps, the conformations and electronic structures of poly(ketene) (PKT) and related polymers have been studied by semiempirical and ab initio quantum chemical methods. The band structure of PKT indicates that the oxygen lone pair bands are very close to the Fermi level independent of the conformation of the polymer. Two related hypothetical polymers, [(COCHCOH)(CH)2]x and [CHCOCHCHCOCH]x, have small band gap values (calculated to be around 1 eV). The small band gaps for these polymers can be attributed to a delocalized oxygen lone pair band lying between the occupied-pi and empty-pi* bands, which creates the lone pair (n)-pi* band gaps. The band width of this lone pair band is large enough (1.5 eV) to allow electrical conduction in this unusual lone pair band upon doping.