Improved Single-Site Chromium Catalysts with Electron Rich Indenyl Ligands for the Formation of Ultrahigh Molecular Weight Polyethylene

Abstract

Quinolyl functionalized indenyl chromium complexes with different substitution patterns were synthesized and evaluated as single site catalysts in ethylene polymerization. Adding substituents like a fused cyclohexyl ring or a Si(CH3)3 group to the indenyl moiety improve complex stability, solubility and catalytic activity compared to the unsubstituted analogues. Furthermore, the ability to incorporate 1-hexene into the polymer chain increased. Ultrahigh molecular weight polyethylene (UHMW-PE) or linear low density polyethylene (LLD-PE) with very high molecular weight was obtained. Although other catalysts are able to incorporate more 1-hexene only a few systems are known, that combine substantial 1-hexene incorporation with very high activity and such high molecular weights. Consequently, these catalytic systems are attractive candidates in industrial processes for the production of improved polyethylene materials.