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

Abstract

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-1,3,6,2dioxazaborocane 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 (Đ < 1.29) in excellent yield (>85%). A detailed investigation of the polymer structures using 1 H 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(3hexylthiophene)-b-poly(benzotriazole).

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

“…Boron moieties were introduced on phenyl‐based acceptors (BTz and QX) instead of heterocycle‐based donors (Th, EDOT, and Se) to maximize the conversion by suppressing protodeboronation [60] . First, BTz‐EDOT monomer (medium A‐strong D) protected with N ‐BnMe 4 DABO ( M1 ), which was recently shown to be an optimal boronate for the SCTP of BTz, [58] was prepared. The conventional SCTP conditions using RuPhos Pd G3 with 4‐iodobenzonitrile as the external initiator at a monomer to initiator ratio (M/I ratio) of 25 and 45 °C produced the desired PBTzEDOT with M n of 11.9 kg mol −1 and narrow Ð (1.07) (Table 1, entry 1).…”

“…Recently, our group developed an efficient SCTP system for a wide range of monomers, including strong D (3,4-propylenedioxythiophene) and A (quinoxaline, QX). [56][57][58][59] The Pd catalyst coordinated by Buchwald ligands such as RuPhos-and SPhos-Pd exhibited extraordinary catalysttransfer ability, achieving a universal polymerization of (hetero)arenes with very distinctive electronic properties by a novel strategy that included utilizing N-coordinated boronates such as 4,4,8,8-tetramethyl-1,3,6,2-dioxazaborocane (Me 4 DABO) and its N-benzylated derivative (N-BnMe 4 DABO). Therefore, this versatility encouraged us to expand the catalytic system to more challenging DA biaryl monomers.…”

Recent progress in organic field‐effect transistor‐based integrated circuits

“…It should be pointed out that in recent years, the understanding of crystal structures of conjugated polymers is going deeper. 62 Moreover, gratifying progress have been made in improving the structural precision and sequence homogeneity of polymers, [63][64] which gives polymers more controllable electronic properties and better charge transport. Seferos and co-workers have developed several polymerization and assembly strategies to obtain conjugated polymers with controlled molecular weight and low dispersity, which is significant in lowering the structural and energetic disorder, and improving charge transport in bulk or thin films.…”

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

“…Recently, our group developed an efficient SCTP system for a wide range of monomers, including strong D (3,4-[*] H. Kim, J. Lee, T. Kim, M. Cho, T.-L. Choi Department of Chemistry, Seoul National University Seoul 08826 (Republic of Korea) E-mail: tlc@snu.ac.kr propylenedioxythiophene) and A (quinoxaline, QX). [56][57][58][59] The Pd catalyst coordinated by Buchwald ligands such as RuPhos-and SPhos-Pd exhibited extraordinary catalysttransfer ability, achieving a universal polymerization of (hetero)arenes with very distinctive electronic properties by a novel strategy that included utilizing N-coordinated boronates such as 4,4,8,8-tetramethyl-1,3,6,2-dioxazaborocane (Me 4 DABO) and its N-benzylated derivative (N-BnMe 4 DABO). Therefore, this versatility encouraged us to expand the catalytic system to more challenging DA biaryl monomers.…”