In 1995, Professor Brookhart successfully polymerized ethylene and copolymerized ethylene with methyl acrylate using alpha-diimine palladium catalysts.[1] However, these catalysts showed very low activity and low thermal stability. Moreover, the obtained polyethylene and copolymer possess very low molecular weight, high branching density and random microstructure, making them oil or wax. Recently, through the modification of ligand's axial hinderance, we can dramatically improve the catalytic activity and thermal stability. Furthermore, we can greatly increase the polymer molecular weight and lower the branching density, thereby generating semicrystalline solid materials. [2] The introduction of even a small amount of polar functional groups into the polyolefins could excise great control over important material properties. As the most direct and economic strategy, the copolymerization of olefin with polar functionalized monomers represents one of the biggest challenges in this field. In this part, we demonstrate that these obstacles could be potentially addressed through rational catalyst design[3]. Copolymers with highly linear microstructure, high melting temperatures and very high molecular weights (close to or above one million) could be generated. The concept of direct synthesis of polar functionalized ultra-high-molecular-weight polyethylene was introduced, which has not been deemed possible previously.

Highly robust Pd(II) α–diimine catalysts for olefin (co)polymerization

253rd National Meeting (2017)

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