Syntheses of polysiloxane-supported zirconocene catalysts and application to ethene polymerization

Polysiloxanes with bisindenyl, bisfluorenyl, and bis(1,2,3,4-tetramethyl)cyclopentadienyl side groups were synthesized by condensation of the corresponding dichlorosilane compounds and water to obtain supported zirconocene catalysts. The polymerization of ethene was conducted over these catalysts combined with methylalumoxane. The polymerization activity depends markedly upon the substituents and decreases in the order: bisindenyl much greater than bisfluorenyl much greater than bis(1,2,3,4-tetramethylcyclopentadienyl). All the supported catalysts give linear polyethene with fairly high molecular weights. The catalyst with bisindenyl groups was found to be composed of a toluene-soluble and a toulene-insoluble fraction. The polymerization profile (activity versus time curve) was analyzed with the toluene-soluble and -insoluble fraction as well as the corresponding homogeneous system. The homogeneous system, which exerts the highest activity in the initial phase, was completely deactivated after several hours whereas the activity of the supported catalyst, especially of the toluene-insoluble fraction, was unchanged during 12 h even at 70 degrees C. Polysiloxanes with different content of bisindenyl groups were also synthesized via the co-condensation with dimethyldichlorosilane and applied as the carrier. However, the activity per Zr atom decreases remarkably with an increase in dimethylsilane units.