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Studies on homo and copolymerizations of long-chained alpha-olefins over metallocene catalysts

Quijada R., Rojas R., Guevara J., Narvaez A., Delfin D., Galland G. B.

Polimery

2000

T. 45, nr 5

339-343

Metallocene catalysts, viz., rac-Et(Ind)2ZrCl2, rac-Me2- Si(Ind)2ZrCl2 and Ph2C(Flu)(Cp)ZrCl2, were studied in homopolymerization of 1-octadecene and the first two were used in copolymerization of ethylene with 1-octadecene. They exhibited different activities and rac-Et(Ind)2ZrCl2 was the most active in the homopolymerization carried out at 70°C. At 30°C, the activities were practically identical. In the copolymerization runs, the catalysts were similarly active, and the Et-bridged catalyst was the more active. The copolymers prepared over rac-Me2- Si(Ind)2ZrCl2 were found to have more comonomer incorporated. The composition of copolymerization products was found (13C-NMR) to vary with the catalyst system. DSC thermograms showed poly-1-octadecene prepared over rac-Et(Ind)2ZrCl2 to vary in properties with polymerization temperature (Figs. 3-5). The homopolymer prepared at 70°C showed endotherms at 41°C and 53°C and that prepared at 30°C produced one broader peak at 67°C. With rac-Me2Si(Ind)2ZrCl2, the 70°C homopolymer produced one broader peaks at 41°C and 53°C and the 30°C homopolymer gave peaks at 7°C and 67°C. The two peaks in the homopolymer thermograms appear to be explicable in terms of different structural ordering in various homopolymer domains. As the comonomer concentration in the feed was increased, the molecular weight decreased and otherwise was independent of the type of the metallocene used.