Precision Synthesis of n-Type π-Conjugated Polymers in Catalyst-Transfer Condensation Polymerization

Recent developments in catalyst-transfer condensation polymerization, which proceeds in a chain-growth polymerization manner, have made it possible to synthesize well-defined pi-conjugated polymers with controlled molecular weight and low polydispersity, as well as block copolymers and gradient copolymers. However, catalyst-transfer condensation polymerization has been limited to the polymerization of donor monomers (such as thiophene) for the synthesis of p-type pi-conjugated polymers. Here, we highlight several recent advances in catalyst-transfer condensation polymerization leading to n-type pi-conjugated polymers. The Kumada-Tamao coupling polymerization of Grignard pyridine monomers yields well-defined poly(pyridine-3,5-diyl) and poly(pyridine-2,5-diyl) with a broad molecular weight distribution. Monomers consisting of strong acceptor and weak donor moieties also undergo catalyst-transfer polymerization; well-defined poly(fluorene benzothiaziazole) was obtained by Suzuki-Miyaura coupling polymerization and poly(bithiophene naphthalene diimide) was obtained by an unusual Ni-catalyzed coupling polymerization of an anion radical generated from a bromothiophene naphathalene diimide bromothiophene monomer and activated zinc.