Polymerization of isobutyl vinyl ether (IBVE) has been studied with mononuclear half-titanocene

CpTiCl3 [1] and dinuclear half-titanocenes

[(C5H4)2(CH2)n][(TiCl3)2] [2 (n = 3)

3 (n = 6)]

and [(C5H4)2(CH2)n][(TiCl2OR)2] (R = 2

6-diisopropylphenoxyl) [4 (n = 3)

5 (n = 6)]

in the presence of methyl aluminoxanes (MAO) as cocatalyst in methylene chloride. The influences of the length of polymethylene brigde and the substitution of aryloxy group at the metal center have been investigated at three polymerization temperature (25οC

－10οC

and －30οC). It was observed that the structure of catalyst displayed significant effects on not only the polymerization behavior but also the properties of the produced polymers. At －30οC it was noted that polymerization catalyzed by dinuclear titanocenes indicated a living character where a linear relation between molecular weight of the polymers and monomer conversion. The catalytic activity decreased in the order of 1 2 4 3 5 whereas the stereoregularity of PIBVE

calculated by racemic dyad value

r

increased in the order of 1 2 3 4 5. The collected polymers have the high molecular weight (1 ×105－3 ×105) and narrow molecular weight distribution (PDI ≤ 2.3). Very interestingly the dinuclear half-titanocenes containing a different bridge and substituent generated the polymers containing a different level of syndiotacticity from 47% to 56% according to the employed catalyst

which clearly demonstrated the property of aryloxy substituent at the metal center played a key role to adjust polymer stereoregularity.