A study of molecular weight regulation in polyethylene by titanium diolate catalysts

Homogeneous titanium(IV) complexes derived from cyclohexanediol formulated as (O∩O)Ti(OPri)2 (1) were used as catalysts for polymerization of ethylene at high temperatures and pressures. In the presence of ethylaluminium sesquichloride co‐catalyst, low‐molecular‐weight polyethylenes with narrow dispersities were obtained. A series of homogeneous titanium(IV) complexes derived from cyclohexanediol were synthesized and characterized. These catalysts, formulated as [Ti–(O∩O)(OR)2], [Ti–(O∩O)OPriCl] and [Ti–(O∩O)2], were found to be highly active in the polymerization of ethylene at high temperature in combination with ethylaluminium sesquichloride (Et3Al2Cl3, EASC) as co‐catalyst. The resultant polyethylene had a low polydispersity index indicating the formation of single‐site catalytic species with molecular weight in the range 639–1036 g mol−1 which was analysed using 1H NMR spectroscopy and found to be linear, suggesting that a chain transfer to the aluminium of EASC occurs. © 2013 Society of Chemical Industry