Electrical anisotropy of orientedtrans-polyacetylene undoped and doped with SO3

Abstract

We use extended Huckel methods of molecular orbitds and crystal orbitals (EHMO/CO) to calculate the two-dimensional band structures of highly oriented trans-polyacetylene (PA) undoped and doped with SO3. According to the energy band theory of solids, we explain the changes of band gap (Eg) and bandwidth (BW) from undoped PA to SO3-doped PA, and discuss the electrical anisotropy of orientedtrans-polyacetylene doped with SO3 The calculated results show that the conductivity anisotropy ratio (σ/σ⊥,) is determined by Eg, and BW in the directions both parallel (σ) and perpendicular (σ⊥,) to the PA chains, respectively. The conductivity anisotropy ratio σ/σ⊥ decreases when PA is doped with SO3, because the dopant plays a conjugated bridge role between the interchains of PA, and makes the dopant itself and PA chains show a strong interchain coupling. The theoretical results for undoped and doped PA are in good agreement with experimental ones.