Short-Chain Branched Polar-Functionalized Linear Polyethylene via “Tandem Catalysis”

Abstract

Cationic Pd^II complex 1 chelated by an N-fixed phosphine sultam has been synthesized and structurally characterized. Exposure of 1 to ethylene resulted in the formation of short-chain olefins (1-butene: 2-butene: 1-hexene: 1-octene = 86:7:6:1) with a high catalytic activity of 10⁵ mol_E mol_Pd^–1 h^–1. By combination of 1 and one of the well-known phosphinesulfonato PdII catalyst precursors 2–5, linear polyethylenes containing methyl, ethyl, and n-butyl branches of up to 100 per 1000 C were generated from the polymerization of ethylene alone in a “tandem catalysis” one-pot approach. In further exploitation of this concept, linear polyethylenes with both various short-chain branches and a choice of different polar functional groups incorporated into the main chain were obtained for the first time from the copolymerization of ethylene and polar vinyl monomers (methyl acrylate, N-isopropylacrylamide, methyl vinyl sulfone, acrylonitrile, ethyl vinyl ether, vinyl acetate, and allyl bromide). All these apolar and polar branches are incorporated into the linear polyethylene backbones to varying degrees, while the type of initiating and terminating chain ends of the resulting polyethylenes depends significantly on the nature of polar vinyl monomer.