Polar additive triggered chain walking copolymerization of ethylene and fundamental polar monomers

Abstract

Copolymerization of ethylene with polar monomers to produce functionalized polyethylenes is important but is a great challenge by using the seminal cationic α-diimine palladium(II) catalyst. A wide range of polar monomers generally shut down the reaction because of the underlying β-X elimination events and formation of stable chelates. In this contribution, a polar additive strategy was developed to overcome these issues. A large excess of a nitrile compound that acted as a polar additive triggered copolymerizations of ethylene with fundamental polar vinyl and allyl monomers, including methyl acrylate, vinyl acetate, butyl vinyl ether, allyl acetate, tert-butyl 3-butenoate, butyl allyl ether, allyl chloride, acrylic anhydride, allyl acrylate, and allyl methacrylate, mediated by one α-diimine palladium(II) catalyst. This avoided a tedious hunting on a one-to-one catalyst. Catalytic activities, copolymer molecular weights, branching densities and microstructures, and co-monomer incorporations could be modulated by varying the amount of the polar additive. Possible mechanistic insights were proposed on the basis of these copolymerization results.