Isotactic polymerization of olefins with metallocene MAO catalysts
Polimery 1997, No 10, 587
Metallocene/tetramethyl aluminoxane (MAO) catalysts control the tacticity and the molecular weight and its distribution in the polymer. Zirconocene and hafnocene catalysts copolymerize ethene with cyclic olefins such as norbomene and dimethanooctahydronaphthalene (DMON) to yield copolymers with the doublebond, rather than the ring, opened to extend the chain. These products are atactic and have interesting properties. Syndiotactic polystyrene, mp as high as 275°C, is another class of tailor-made (titanocene/MAO)-catalyzed polymers. With the fluorinated (CpTiF3) substituted for the chlorinated (CpTiCl3) titanocenes, the activity rose by a factor of 5-30. The two types of polymers were studied with numerous metallocenes used ascatalysts. Nine metallocenes were used to study their activity in the copolymerization of ethylene with cyclo olefins. The reactivities of comonomers were established in the ethylene—DMON systems catalyzed by zircono- and hafnocenes.Titanocenes proved to be much more active than the systems involving alkoxy-derivatives Ti(OR)4 .