Electronic structure of poly(p-phenylene) - poly(acetylene) copolymers

Abstract

Summary form only given. We investigate theoretically the electronic structure of statistical and block copolymers of poly(p-phenylene) [PPP] and poly(acetylene) [PA]. The calculations are performed using the Negative Factor Counting (NFC) technique coupled to the Valence Effective Hamiltonian (VEH) method. We analyze the degree of spatial localization of the upper occupied and lower unoccupied levels from the wavefunctions calculated by means of the Inverse Iteration technique. As a consequence of the energy gap difference calculated for the parent polymers, the bandgap of PA/PPP copolymers can be tuned over the whole visible range depending on the relative concentrations and distributions of PA and PPP segments. An important result is the formation of spatially localized frontier orbitals within the PA moieties when these: segments cluster. Consequently, the bandgap energy strongly decreases compared to those obtained for statistical copolymers presenting similar PA/PPP relative concentrations.