Recently longer chains of polyketene, which is a variant of trans-polyacetylene (t-PA) where every second hydrogen atom is substituted by a hydroxyl group, have been synthesized. We performed minimal-basis-set ab initio band-structure calculations on polyacetylene and polyketene. In agreement with experimental findings, we found that the fundamental gap of the polymer does not change due to substitution of H by OH. Soliton dynamics within the Su-Schrieffer-Heeger Hamiltonian in polyketene shows a moving soliton in this system, however, with a reduced velocity compared to t-PA. Together with our previous results that a C?O group in a t-PA chain behaves as a soliton trap and the fact that ≊30% of the CO groups in polyketene are in the keto form instead of the enol form, we can explain the experimental findings of both localized and mobile spins in this material.

• Received 17 December 1990

DOI:https://doi.org/10.1103/PhysRevB.43.13938