| abstract |
This invention is for a method for varying the melting pointsnand molecular weights of syndiotactic polyolefins by usingnmetallocene catalysts with substituents on the aryl rings of anfluorene ligand in certain positions. Electron donatingnsubstituents, for example, dialkylamino, halogen, and alkoxyngroups, when present on fluorene at C1, C2, C3 or C2 and C7 rendernthe catalyst less active and decrease the polymer molecular weight.nElectron donating substituents, such as alkyl, dialkylamino,nhalogen or alkoxy, at C4 not only increased the catalyst efficiencynbut also dramatically increased the polymer molecular weight.nBulky hydrocarbyl substituents, such as alkyl, cycloalkyl and arylngroups, at C2 and C7 increase the melting point. Bulkynsubstituents such as hydrocarbyl groups like alkyl, cycloalkyl,naryl, alkoxy and dialkylamino groups etc., at C4/C5 decrease thenmelting point. When multiple substituents are present on fluorene,ntheir effects are additive. |