Precision Synthesis of Various Low-Bandgap Donor-Acceptor Alternating Conjugated Polymers via Living Suzuki-Miyaura Catalyst-Transfer Polymerization.

Herein, we demonstrate that living Suzuki-Miyaura catalyst-transfer polymerization (SCTP) using a RuPhos Pd G3 precatalyst is a versatile method for the precision synthesis of various donor-acceptor alternating conjugated polymers (DA ACPs). First, the living SCTP of biaryl monomers with combinations of both medium to strong A and D were optimized to produce DA ACPs with controlled number average molecular weight (Mn ), narrow dispersity (Ð, 1.05-1.29), and high yield (>87 %). Moreover, its expansion to controlled polymerization (Mn =9.2-40.0 kg mol-1 ) of an A1 -D-A2 -D quateraryl monomer containing diketopyrrolopyrrole (DPP; strong A) was successful. The living SCTP also enabled the efficient one-pot synthesis of various diblock and triblock copolymers. Lastly, the DA ACPs showed tunable optical band gap (Eg opt , from 1.29 to 1.77 eV) and highest occupied molecular orbital (HOMO) level (from -5.57 to -4.75 eV), while their block copolymers exhibited broad absorption ranges and promising visible light-harvesting properties.

Universal Suzuki-Miyaura Catalyst-Transfer Polymerization for Precision Synthesis of Strong Donor/Acceptor-Based Conjugated Polymers and Their Sequence Engineering.

Catalyst-transfer polymerization has revolutionized the field of polymer synthesis due to its living character, but for a given catalyst system, the polymer scope is rather narrow. Herein we report a highly efficient Suzuki-Miyaura catalyst-transfer polymerization (SCTP) that covers a wide range of monomers from electron-rich (donor, D) to electron-deficient (acceptor, A) (hetero)arenes by rationally designing boronate monomers and using commercially available Buchwald RuPhos and SPhos Pd G3 precatalysts. Initially, we optimized the controlled polymerization of 3,4-propylenedioxythiophene (ProDOT), benzotriazole (BTz), quinoxaline (QX), and 2,3-diphenylquinoxaline (QXPh) by introducing new boronates, such as 4,4,8,8-tetramethyl-1,3,6,2-dioxazaborocane and its N-benzylated derivative, to modulate the reactivity and stability of the monomers. As a result, PProDOT, PBTz, PQX, and PQXPh were prepared with controlled molecular weight and narrow dispersity (D < 1.29) in excellent yield (>85%). A detailed investigation of the polymer structures using 1H NMR and MALDI-TOF spectrometry supported the chain-growth mechanism and the high initiation efficiency of the SCTP method. In addition, the use of RuPhos-Pd showing excellent catalyst-transfer ability on both D/A monomers led to unprecedented controlled D-A statistical copolymerization, thereby modulating the HOMO energy level (from -5.11 to -4.80 eV) and band gap energy (from 1.68 to 1.91 eV) of the resulting copolymers. Moreover, to demonstrate the living nature of SCTP, various combinations of D-A and A-A block copolymers (PBTz-b-PProDOT, PQX-b-PProDOT, and PQX-b-PBTz) were successfully prepared by the sequential addition method. Finally, simple but powerful one-shot D-A block copolymerization was achieved by maximizing the rate difference between a fast-propagating pinacol boronate donor and a slow-propagating acceptor to afford well-defined poly(3-hexylthiophene)-b-poly(benzotriazole).