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

Abstract

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).