Ethylene polymerization by diphenyl ether bridged dinuclear titanocenes/MAO

Two diphenyl ether bridged dinuclear titanocenes, (C 5 H 5 TiCl 2 ) 2 {[(RC 5 H 3 )CH 2 ]( p ‐C 6 H 4 )O(C 6 H 4 ‐ p ) [CH 2 (C 5 H 3 R)] [R = H( 5 ), Me( 6 )] have been synthesized and characterized by 1 H‐NMR spectroscopy and elemental analysis. In the presence of methylaluminoxane (MAO), 5 and 6 are efficient catalysts for ethylene polymerization. The influences of the polymerization conditions such as [MAO]/[Cat] molar ratio, catalyst concentration, polymerization temperature and time have been studied in detail. Compounds 5 and 6 produce 10 5 g polyethylene (PE)/(mol Ti h), which is in the same range as that produced by the binuclear titanocenes {(C 5 H 5 TiCl 2 ) 2 [(C 5 H 4 CH 2 ) ( p ‐C 6 H 4 )(C 6 H 4 ‐ p )(CH 2 C 5 H 4 )]} ( 7 ) and (C 5 H 5 TiCl 2 ) 2 (C 5 H 4 CH 2 CH 2 OCH 2 CH 2 C 5 H 4 ) ( 8 ). However, the molecular weight of PE is somewhat higher than that of PE using 7 and 8 . The high temperature gel permeation chromatography (GPC) results show that the molecular weight distributions of PE produced by 5 and 6 (MWD = 6.17 and 7.56) were obviously broader than those of PE produced by 7 (MWD = 4.28) and 8 (MWD = 5.90). The melting points of the PE produced by 5 and 6 are higher than 132°C, indicating ahighly linear and highly crystalline PE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008