Ethylene polymerization by 3‐oxa‐pentamethylene bridged asymmetric dinuclear titanocene/MAO system

Abstract

Abstract An asymmetric 3‐oxa‐pentamethylene bridged dinuclear titanocenium complex (CpTiCl 2 ) 2 (η 5 ‐η 5 ‐C 9 H 6 (CH 2 CH 2 OCH 2 CH 2 )C 5 H 4 ) ( 1 ) has been prepared by treating two equivalents of CpTiCl 3 with the corresponding dilithium salts of the ligand C 9 H 7 (CH 2 CH 2 OCH 2 CH 2 )C 5 H 5 . The complex 1 was characterized by 1 H‐, 13 C‐NMR, and elemental analysis. Homogenous ethylene polymerization catalyzed using complex 1 has been conducted in the presence of methylaluminoxane (MAO). The influences ofreaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results show that the catalytic activity and the molecular weight (MW) of polyethylene produced by 1 /MAO decrease gradually with increasing the catalyst concentration or polymerization temperature. The most important feature of this catalytic system is the molecular weight distribution (MWD) of polyethylene reaching 12.4, which is higher than using common mononuclear metallocenes, as well as asymmetric dinuclear titanocene complexes like [(CpTiCl 2 ) 2 (η 5 ‐η 5 ‐C 9 H 6 (CH 2 ) n C 5 H 4 )] ( n = 3, MWD = 7.31; n = 4, MWD = 6.91). The melting point of polyethylene is higher than 135°C, indicating highly linear and highly crystalline polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008