Living polymerization of propylene with heteroligated phenoxyimine titanium complexes: Combining extremely high activity with high syndiospecificity

A series of 60 new heteroligated bis(phenoxyimine) titanium(IV) complexes bearing halogen substituents on the phenolate rings were synthesized and screened as catalysts for propylene polymerization. Upon activation with MAO, complexes exhibited extremely high catalyst activity up to 210,000 molPP/molTi•h at 0°C. The resulting polypropylenes have very high molecular weights with narrow molecular weight distributions. 49 catalysts are capable of catalyzing living syndioselective propylene polymerization. Microstructure analyses by 13C NMR spectroscopy revealed that the resulting polypropylenes are syndio-enriched with rr content in the range of 62-97%, and a chain-end control mechanism is responsible for the observed syndiotacticity. The electron-withdrawing halogen substituents on the phenolate moiety and electron-withdrawing substituents on the N-aryl moiety had significant effect on the activity and the syndioselectivity of propylene polymerization. The catalyst activity increases with the electronegativity of the halogen substituents. The syndiotacticity of the produced polypropylenes increases as the size of the ortho-halogen substituents is increased. Polymerization conditions such as catalyst concentration, polymerization time, polymerization pressure, polymerization temperature also have profound effects on the catalyst activity and the properties of polypropylenes.;Supported heteroligated phenoxyimine (PHI) titanium catalysts were prepared by immobilizing 4 extremely active homogenous heteroligated Ti-PHI catalysts on MAO modified silica. The silica/MAO supported catalysts were evaluated for propylene polymerization upon activation by MAO at ambient temperature. The activities of the immobilized Ti-PHI catalysts are much lower than those of their homogenous analogues and are influenced by polymerization temperature, silica calcination temperature, Al content on the support, and Ti loading on the support.;Finally we applied homoligated Ti-PHI catalysts on the copolymerization of propylene with polar vinyl monomers such as methyl acrylate and methyl vinyl ketone. Maximum incorporations of 21.2 mol % of MA and 3.4 mol % of MVK in the syndiotactic polypropylene backbones were achieved. Copolymers were characterized by 1H, 13C NMR and FT-IR spectroscopy and GPC.