Direct Arylation Polycondensations: Emerging Protocols for the Synthesis of High-Performance Polymer Semiconductors

Direct arylation polycondensations (DArP), including the DArP of C─Br and C─H monomers and oxidative DArP of C─H monomer(s), are characterized by their atom economy and simplicity compared with conventional transition-metal-catalyzed polycondensations. In the past decade, DArP have emerged as promising protocols for synthesizing high-performance polymer semiconductors used in organic thin-film transistors (OTFTs), organic solar cells (OSCs), organic electrochemical transistors (OECTs), etc. Several existing high-performance polymer semiconductors with high molecular weight and low structural defects have been successfully synthesized via optimizing the polymerization conditions of C─Br/C─H DArP, achieving device performances comparable to or even exceeding the counterparts obtained from conventional methods. Particularly, new C─H monomers, such as β-halogenated thiophene derivatives and 5-thiazoyl-terminated aryls, have been designed with consideration of both the enhancement of C─H-bond reactivity and semiconducting properties of the resulting polymers, enabling the synthesis of novel conjugated polymers with superior semiconducting properties via DArP as efficient as conventional protocols such as Stille and Suzuki polycondensations. In this article, we summarize the progress in high-performance polymer semiconductors synthesized via DArP as mentioned above and discuss mechanistic insights underlying the improved polymerization outcomes.