Achieving ultra‐high molecular weight polyethylenes by vanadium aroylhydrazine‐arylolates

Abstract

A series of vanadium(V) aroylhydrazine-arylolates is employed in ethylene polymerization to produce ultra-high molecular weight polyethylene (UHMWPE), surprisingly extending to such coupling reactions beyond their common usage in the oxidation of hexanes and alcohols. Activated by either MAO or DMAC, the complexes V1-V3 efficiently catalyze the polymerization of ethylene into UHMWPE, that is, with an activity up to 3.37 Â 10 6 g mol À1 h À1 (60 C) and the polyethylene obtained has a molecular weight around 3 million g mol À1 , being the highest molecular weight achieved by a vanadium catalyst so far. More importantly, the significant effects of different cocatalysts are well illustrated; the catalytic system with MAO generally shows lower activity with almost one order in the magnitude than that with DMAC (0.43 vs. 3.37 Â 10 6 g mol À1 h À1 ), but the polyethylenes with higher molecular weights are obtained by the system with MAO.

Vanadium Complexes Derived from O,N,O-tridentate 6-bis(o-hydroxyalkyl/aryl)pyridines: Structural Studies and Use in the Ring-Opening Polymerization of ε-Caprolactone and Ethylene Polymerization

“…Some promising results have been achieved by combining such chelates with the metal vanadium, which is the 20th most abundant metal in the Earth's crust. In particular, we and others have found that very high catalytic activities and thermally robust systems are accessible for α-olefin polymerization when conducted in the presence of co-catalysts such as dimethylaluminium chloride and the re-activator ethyl trichloroacetate [19][20][21][22][23][24][25][26][27][28][29][30][31], as well as ethylene copolymerization with the likes of propylene, 1-hexene or norbonene [32][33][34][35][36][37][38][39][40][41]. Moreover, a number of vanadyl-containing systems have shown promise in the ROP of cyclic esters [42,43], whilst other systems have been shown to be promising for both ROP and α-olefin polymerization [44][45][46][47][48][49].…”