Rotational Effect on the One-Dimensional π-Conjugated Polymer

We have investigated the modulation of the physical and electronic properties including their band structure of poly(1,4-phenylene diethynylene-co-9,10-anthracenylene) by the co-axial rotation of π-conjugated polymer chain in the periodic boundary condition framework. The estimated rotational barrier was calculated to 2.38 kcal/mol per cell, suggesting that the aromatic rings of phenylene and anthracenylene were freely rotating each other at the room temperature. On the other hand, bandgap dramatically changes 2.0–3.0 eV by the rotation of aromatic rings. This result suggests that the electronic properties of this polymer should be influenced by rotational effect at the ambient condition.