Precision Synthesis of Ethylene and Polar Monomer Copolymers by Palladium-Catalyzed Living Coordination Copolymerization

Abstract

Coordination insertion polymerization is unsurpassed as a straightforward method for synthesis of high-value polyolefins by the copolymerization of ethylene and polar monomers, but poison effects of polar groups on the metal center result in a lack of fine control over the polymer architecture. Herein we reported a thermally stable dibenzobarrelene-derived α-diimine palladium catalyst for the precision synthesis of functionalized polyolefins by living copolymerization of ethylene and a variety of acrylate comonomers. The introduction of the bulky dibenzobarrelene backbone can improve migratory insertion selectivity of methyl acrylate (MA) in a 2,1-mode, thus preventing polar groups from poisoning palladium centers by stable five-membered palladacycle intermediates formed by 1,2-insertion of MA. In this living chain-walking catalyst system, the composition, molecular weight, and branching topology of the copolymer can be facilely tunable by simple variation of the ethylene pressure.