| Abstract: | The syndiotactic polymerizations of styrene are carried out with dinuclear titanocenes such as tetramethyldisiloxanediylbis(cyclopentadienyltitanium trichloride), Cl3Ti-CpSi(CH3)2-O-Si(CH3)2Cp-TiCl3 (1), hexamethyltrisiloxanediylbis(cyclopentadienyltitanium trichloride), Cl3Ti-CpSi(CH3)2-O-Si-(CH3)2-0-Si(CH3)2Cp-TiCl3 (2) and hexamethyl-trisiloxanediylbis(dicyclopentadienyltitanium dichloride), Cl2CpTi-CpSi(CH3)2-O-Si-(CH3)2-O-Si(CH3)2Cp-TiCpCl2 ( 3 ) in the presence of modified methylaluminoxane (MMAO). Although the catalyst activity of dinuclear titanocenes is lower than that of the corresponding mononuclear titanocenes CpTiCl3 and Cp2TiCl2, the former produce polystyrene of higher weight-average molecular weight and higher syndiotactic index than the latter. Among the dinuclear titanocenes examined, 2 has the largest catalyst activity. In addition, the copolymerizations of styrene and ethylene are carried out with 2 . |
