Fluorinated Bis(phenoxyketimine)titanium Complexes for the Living, Isoselective Polymerization of Propylene: Multiblock Isotactic Polypropylene Copolymers via Sequential Monomer Addition
journal contributionposted on 09.04.2008, 00:00 by Joseph B. Edson, Zhigang Wang, Edward J. Kramer, Geoffrey W. Coates
A series of bis(phenoxyketimine)titanium dichloride complexes were synthesized and evaluated as catalysts for living, isoselective propylene polymerization upon activation with methylaluminoxane (MAO). Catalysts bearing phenoxyketimine ligands with different substituents at the ortho and para positions of the phenolate ring and substituents at the ketimine carbon were investigated. The identity of the ketimine substituent had the largest effect on the activity and isoselectivity of propylene polymerization. Complex 12/MAO promoted the living, isoselective polymerization of propylene ([m4] = 0.73, α = 0.94). This catalyst system was used for the synthesis of a number of block copolymers featuring isotactic polypropylene semicrystalline blocks and poly(ethylene-co-propylene) amorphous blocks. Several triblock samples with varying block lengths, a pentablock, and a heptablock copolymer were synthesized. Mechanical testing has revealed that each is elastomeric with elongations at break between ∼790−1000%.
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propylene polymerizationphenolate ringisoselective propylene polymerizationMAOpara positionsketimine carbonisoselective polymerizationcatalyst systemSeveral triblock samplesMechanical testingSequential Monomer AdditionA seriesphenoxyketimine ligandsheptablock copolymerketimine substituentblock lengthsIsoselective Polymerizationblock copolymersisotactic polypropylene semicrystalline blocks