Orthometallated hafnium pyridyl-amido complexes were first developed as catalysts for the high-temperature solution production of isotactic polypropylene (iPP). However, due to the unique mechanism of catalyst activation, the resulting polymers have broad dispersities. For this reason, the catalysts are not suitable for the preparation of well-defined block copolymers. We have developed Cs-symmetric complexes (1) by modifying the pyridylamido ligand backbone. These precatalysts are active for the living, isospecific polymerization of propylene and the living polymerization of ethylene at ambient temperature and are suitable for the preparation of multiblock copolymers. Multiblock copolymers containing well-defined blocks of polyethylene (PE) and iPP were prepared and the molecular weight of the individual blocks and the total number of blocks were varied systematically. The tetra- and hexablock copolymers were found to be useful compatibilizers for blends of PE and iPP.

New applications for hafnium pyridylamido catalysts

2019 Spring National Meeting

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