Ethylene polymerization with novel phenoxy-imine catalysts bearing 4-vinylphenyl group

This contribution reports ethylene polymerization behavior of titanium complexes incorporating bis(phenoxyimine) ligands. Six phenoxy-imine Ti(IV) complexes {6-R ¹ -2-CH=N(2,6-difluoro-3,5-diR ² -4-R ³ Ph)]C₆H₃O}₂TiCl₂ (1: R₁ = H, R₂ = H, R₃ = H; 2: R¹ = H, R² = H, R³ = 4-vinylphenyl; 3: R¹ = CH₃, R² = H, R³ = H; 4: R¹ = CH₃, R² = H, R³ = 4-vinylphenyl; 5: R¹ = CH₃, R² = F, R³ = H; 6: R¹ = CH₃, R² = F, R³ = 4-vinylphenyl) have been synthesized and evaluated for ethylene polymerization using dried MAO (simplified as DMAO) as cocatalyst. An obvious catalytic heterogeneity of Cat 2 (Complex 2/DMAO) towards ethylene polymerization was observed, which was illustrated by decreased activity, multimodal molecular weight distribution and partially improved particle morphology comparing with Cat 1. Moreover, Cat 3 exhibits “living” characteristics in the process under certain conditions (25 °C, less than 20 min). Otherwise, the moderate to high ethylene polymerization activity of ca. 10⁵–10⁶ g PE/(mol Ti·h) and high molecular weight (M _w = 10⁵–10⁶) of polyethylene can be obtained by changing the skeleton structure of these complexes.