Synthesis of Long-Chain Branched Comp-Structured Polyethylene from Ethylene by Tandem Action of Two Single-Site Catalysts

The synthesis of long-chain branched polyethylene by copolymerization of ethylene with higher α-olefins has its limitations due to commercial availabilities of pure α-olefins above carbon lengths of C30. Soga 1 and Bazan 2 have shown the possibility of inserting side chains up to a length of 60 carbons into a growing polyethylene backbone. The details of combining [Me 2 C(Cp) 2 ]ZrCl 2 (1) and [Me 2 Si(N t Bu)(Me 4 Cp)]TiCl 2 (2) to obtain long-chain branched polyethylene with branch lengths up to 350 carbons as well as the copolymerization profile and purification of the product throughout the Kumagawa extraction are discussed here. Compound 1 was used in a first oligomerization step to yield a macro-comonomer. Three different methods involving conventional copolymerization, tandem polymerization, and simultaneous entry of the catalysts were examined using 2 and MAO as cocatalyst to copolymerize different macro-comonomers with ethylene.