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

Cationic
PdII 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 molE molPd–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.