Tailoring Hexagonal Gibbsite Single Crystal Nanoplatelets for Ethylene Polymerization and Nanocomposite Formation on MAO-Free Heterogeneous Bis(imino)pyridine Iron(II) Catalyst

Ultrathin single crystal.-Al(OH) 3 (Gibbsite) nanoplatelets with average thickness < 20 nm and length < 800 nm, pretreated with trimethylaluminum (TMA), represent highly efficient activators and supports bis(imino) pyridine iron (II) (FeBIP) complex to produce high density polyethylene (HDPE) as well as gibbsite/HDPE nanocomposites in exceptionally high yields. Opposite to both methylaluminoxane (MAO)-activated homogeneous FeBIP catalyst and heterogenous silica-supported single site catalysts, no addition of MAO is required. At low TMA/Fe >= 50 molar ratio, the superior catalyst activity (up to 6500 kg mol(-1) h(-1) bar(-1)) of FeBIP@TMA@Gibbsite is paralleled by controlled polyethylene particle growth without encountering reactor-fouling problems typical for homogeneous catalysts. TMA@ Gibbsite is compared with other AlR3@Gibbsite activators. The Al/Fe molar ratio governs catalyst activity as well as molar mass, molar mass distribution, and thermal properties of polyethylene. Moreover, hexagonal gibbsite nanoplatelets are uniformly dispersed in polyethylene to yield agglomerate-free polyethylene/gibbsite nanocomposites.