Leaching- and fragmentation-free heterogenization of late transition metal complexes as a model system to prove the growth mechanism of polyethylene

Abstract

Adopting a leaching- and fragmentation-free protocol, Ni(II) α-diimine complexes were covalently anchored on nonporous silica without any conventional tedious process. The supported catalysts polymerized ethylene with activities > 10⁶ g-PE mol-Ni⁻¹ h⁻¹ bar⁻¹ (10 kg-PE g-cat⁻¹ at 5.5 bar pressure) when activated with a small amount (Al/Ni ∼100) of common aluminium alkyls (ethylaluminium sesquichloride, methylaluminium dichloride, and diethylaluminium chloride) in the absence of any methylaluminoxane. The polymer growth pattern from uniform spheres to fibers was clearly traced by using this model supported system, which depends on the catalytic activity, metal loading, and effective selection of co-catalysts. The polymerization results were compared with conventional porous silica supports immobilized by the same complex that undergoes fragmentation leading to a poor PE morphology.