The Quantum Chemistry Research of Polyenes. Part I. Conductivity of Polyacetylene (Polyethyne)

The conductivity of polyacetylene has been investigated by using DFT quantum chemical computation of the polyacetylene (PA) oligomers’ bandgap with B3LYP1/def2-TZVP level of theory. The higher conductivity of the PA trans-isomer compared to the cis-isomer was confirmed. It was found that increasing the conjugation length of PA units asymptotically leads bandgap to a value of 1.26 eV for trans-isomer and 2.01 eV for cis-isomer respectively. Dramatical effect of doping on the PA conductivity was proven. This communication discusses the effects of doping by oxidation/reduction of PA (p/n doping), as well as by bromination and deprotonation. The good insulation property of polytetrafluoroethylene (PTFE) was also confirmed. An approach to find out the optimal dopant for best PA conductivity has been proposed at the later stage.