Binuclear nickel catalysts enable one-step copolymerization of ethylene with 2-allylphenol to phenol-functionalized branched polyethylenes

Abstract

One-step ethylene copolymerization with readily available short-chain alkenyl phenols is an attractive alternative to post-modification or the use of designed phenolic comonomers for preparing phenol-functionalized polyethylenes, yet prior examples have largely relied on early transition-metal catalysts or phosphine–sulfonate Pd systems and typically afford linear backbones. Here we report binuclear Ni-catalyzed ethylene copolymerization with 2-allylphenol enabled by Et₂AlCl, which serves as both a cocatalyst and an effective pretreatment reagent for the protic comonomer. Under 1 atm ethylene, phenol-functionalized branched polyethylenes are obtained with activities up to 1200 kg (mol cat h atm)⁻¹, M_n = 19.1–84.1 kg mol⁻¹, phenolic incorporation of 0.5–2.7 mol%, and branching densities of 78–99 CH₃/1000C. Varying Et₂AlCl pretreatment, comonomer concentration and temperature reveals coupled trade-offs between incorporation and productivity/M_n. NMR analysis further reveals both in-chain and chain-end incorporation motifs of the phenolic comonomer.