Chemical modification and doping of poly(p-phenylenes): A theoretical study

Conjugated polymers (CPs) have been recognized as promising materials for the manufacture of electronic devices. However, further studies are still needed to enhance the electrical conductivity of these type of organic materials. The two main strategies for achieving this improvement are the doping process and chemical modification of the polymer chain. Therefore, in this article, we conduct a theoretical investigation, employing DFT calculations to evaluate the structural, energetic, and electronic properties of pristine and push-pull-derived poly(p-phenylene) oligomers (PPPs), as well as the analysis at the molecular level of the polymer doping process. As a primary conclusion, we determined that the PPP oligomer substituted with the push-pull group 4-EtN/CNPhNO₂ exhibited the smallest HOMO-LUMO gap (E_g) among the studied oligomers. Moreover, we observed that the doping process, whether through electron removal or the introduction of the dopant anion ClO₄^-, led to a substantial reduction in the E_g of the PPP, indicating an enhancement in the polymer's electrical conductivity.

DFT calculations were conducted using the PBE0 functional along with the Pople's split valence 6-31G(d,p) basis set, which includes polarization functions on all atoms (B97D/6-31G(d,p)).