Challeges in Chain-Shuttling Polymerization: Novel Ethylene-Norbornene Copolymers and vs Commercial Ethylene-1-octene Copolymers

Advances in polymerization catalysis have allowed the production of olefin block copolymers. Recently, the chain-shuttling copolymerization of two different monomers by two Group 4 metal catalysts that show different monomer selectivities has emerged as a powerful technology for the preparation of olefin block copolymers with different segments.1 The success of chain-shuttling copolymerization reported to date has been limited mostly to the copolymerization of ethylene and propylene (or 1-hexene). In contrast the potential of chain-shuttling copolymerization of norbornene and ethylene in such chain-shuttling copolymerization has remained unexplored to date. The copolymerization of ethylene (E) and norbornene (N) by ansa-metallocene-based catalysts, first reported by Kaminsky, yields amorphous materials with a unique combination of properties, such as high-glass clarity, good solvent resistance, high thermal stability, facile processability, and glass transition temperatures. They are materials of high commercial interest successfully used for applications in optics, capacitor films, food and drug packaging, medical and diagnostic containers. We report herein on copolymerization of norbornene and ethylene by two different ansa metallocene catalysts which show different monomer selectivity and stereoselectivity, with ZnEt2 as a chain-shuttling agent in order to further expand physical properties of E-N copolymers and to widen their applications. Moreover, in order to develop structure-property relationships in the olefin multiblock copolymers we will report also on analysis of elastomeric performances of unfractioned and fractioned commercial ethylene-1-octene copolymers by chain-shuttling polymerization.