Functionalized Polyethylene via ADMET Model Copolymers of Ethylene and Vinyl Monomers

Functionalized Polyethylene via ADMET Model Copolymers of Ethylene and Vinyl Monomers 

Post-polymerization fimctionalization has been used to this end, but most research has been directed toward the copolymerization of ethylene with polar monomers. In this manner, inexpensive monomers can be used to create novel polymeric materials with a wide range of applications. The major drawback to this methodology is the inherent difference in reactivity between ethylene and other vinyl monomers during chain polymerization. This phenomenon is known to yield copolymers with low polar monomer incorporation and increased branch content arising from chain transfer events caused by side reactions with polar and/or protic functionaUties [45]. 

Historically, high-pressure free radical copolymerization has been used to produce highly branched, ill-defined copolymers of ethylene and various polar monomers. Although these materials are in production and extensively used throughout the world, the controlled incorporation of polar functionality coupled with linear polymer structure is still desired to improve material properties. Recent focus in this area has led to the development of new transition metal catalysts for ethylene copolymerization however, due to the electro-philicity of the metal centers in these catalysts, polar functional groups often coordinate with the metal center, effectively poisoning the catalyst. There has b een some success, but comonomer incorporation is hard to control, leading to end-functionalized, branched polyethylenes [44, 46]. These results are undesirable due to low incorporation of polar monomer into the polymer as well 

ADMET offers a synthetic route to strictly linear, fimctionalized polyethyl-enes through the polymerization of a,co-dienes followed by exhaustive hydrogenation. Researchers have been able to use metathesis catalysts in conjimction with the functionalized monomers to produce statistical or sequenced copolymers of ethylene with various polar monomers. With the improved tolerance and reactivity of [ Ru], the broadening of ADMET methodology will allow the syntheses of numerous functionalized systems [4]. However, due to the well known olefin isomerization that occurs during the metathesis polymerization with [Ru], monomer sequence control is lost and the methylene run length between functional groups varies widely. 

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