Ethylene polymerization by diphenyl ether bridged dinuclear titanocenes/MAO

Two diphenyl ether bridged dinuclear titanocenes, (C5H5TiCl2)(2){[(RC5H3)CH2](p-C6H4)O(C6H4-p) [CH2(C5H3R)] [R = H(5), Me(6)] have been synthesized and characterized by H-1-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 105 g polyethylene (PE)/(mol Ti h), which is in the same range as that produced by the binuclear titanocenes {(C5H5TiCl2)(2)[(C5H4CH2) (p-C6H4)(C6H4-p)(CH2C5H4)]} (7) and (C5H5TiCl2)(2)(C5H4CH2 CH2OCH2 CH2C5H4) (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 degrees C, indicating a highly linear and highly crystalline PE. (C) 2008 Wiley Periodicals, Inc.