Low-Temperature Direct Arylation Polymerization for the Sustainable Synthesis of a Library of Low-Defect Donor-Acceptor Conjugated Polymers via Pd/Ag Dual-Catalysis

Donor-acceptor alternating conjugated polymers (D-A CPs) are one of the best materials for high-performance organic electronic devices, owing to their low bandgap and high charge carrier mobility. However, most of the D-A CPs are synthesized by less sustainable polymerization methods. To address this issue, direct arylation polymerization (DArP), eliminating the need for transmetalating agents, was developed over the past two decades. Nevertheless, C-H activation during DArP still requires significantly harsh reaction conditions, limiting the precision and applicability of CPs. In this report, we demonstrate a versatile and sustainable Pd/Ag dual-catalytic DArP conducted at low or even room temperatures, thereby yielding low-defect D-A CPs. Initially, electron-deficient acceptor substrates with various electronic properties and pK_a underwent successful concerted-metalation-deprotonation (CMD) via Ag catalysis with mild conditions and highly chemoselective Pd-catalyzed C-C coupling. This synergistic dual-catalysis allowed for the library synthesis of D-A and A-A CPs from acceptor C-H monomers and aryl halide monomers at low temperatures (25-70 °C) in sustainable solvents such as p-cymene. Interestingly, the D-A CPs obtained via Pd/Ag DArP displayed higher structural regularity and crystallinity, eventually outperforming those prepared by conventional synthetic methods in device performances of ambipolar organic field-effect transistors (μ_e up to 0.80 cm² V^-1 s^-1) and complementary metal-oxide semiconductor inverters (gain up to 102).