Beyond conformational control: effects of noncovalent interactions on electronic properties of conjugated polymers

Noncovalent intramolecular interactions have been often used as conformational control to enhance the planarity of polymers or molecules. However, it is little known if noncovalent interactions may alter the electronic properties of conjugated polymers through some mechanism other than the conformational control. Here, we studied the effects of six common noncovalent interactions on electronic properties of polymers with planar geometry using unconstrained and constrained density functional theory. We found that the sulfur-nitrogen intramolecular interaction may reduce the band gaps of polymers and enhance the charge transfer more obviously than other noncovalent interactions. Our findings are also consistent with the experimental data. For the first time, our study shows that noncovalent interactions may directly affect the electronic structure of polymers, which is not due to the enhancement of molecular planarity. Our work suggests a new mechanism to manipulate the electronic properties of polymers to design high-performance small-molecule-polymer and all-polymer solar cells.