Diversifying peripheral aromatic units of pyrrolo[3,2-b]pyrrole-containing conjugated polymers and the resulting optoelectronic properties

Abstract

Utilizing synthetically simple monomers to create conjugated polymers with tailorable properties is important for the continued development of materials suited for organic electronics. Pyrrolo[3,2-b]pyrrole (DHPP) has been shown to reduce the synthetic complexity commonly associated with conjugated polymers but tailoring properties were limited to the choice of comonomer that is coupled with phenyl-containing DHPPs. Here, the DHPP monomer toolbox is diversified to include thienyl and benzothiadiazole aromatic units directly attached to the periphery of DHPP monomers. Dibrominated monomers are polymerized via Suzuki cross-coupling polymerizations to generate a series of DHPP “homopolymers” with tailorable optoelectronic properties. While phenyl- and thienyl-containing polymers demonstrate localized excitation properties, the benzothiadiazole-containing DHPP polymer exhibits charge-transfer character associated with donor–acceptor materials. These differences in the aromatic unit enable optical absorbances to be tuned across the visible spectrum and provide design guidelines for attaining electrochemically stable DHPP polymers. In addition to fundamental insights into the structure–property relationships of DHPP-based polymers, the synthetic simplicity and tailorability of DHPPs continue to motivate using these building blocks in conjugated materials for optical and electronic devices.