Ethene/Propene Copolymerization from Metallocene-Based Catalytic Systems:  Role of the Alumoxane

• Published in: Macromolecules 1999-01, Vol.32 (2), p.258-263
• Main Authors: Galimberti, Maurizio, Destro, Mara, Fusco, Ofelia, Piemontesi, Fabrizio, Camurati, Isabella
• Format: Article
• Language: English
• Subjects: Applied sciences; Copolymerization; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma980977c

Ethene/propene copolymerizations were performed with a catalytic system composed of a metallocene and an alumoxane. The role played by the alumoxane was investigated by comparing the effects of three different compounds:  poly(methylalumoxane) (MAO), tetraisobutylalumoxane (TIBAO), and tetraisooctylalumoxane (TIOAO). A thorough comparison was performed using rac-ethylenebis(tetrahydroindenyl)zirconium dichloride (r-EBTHIZrCl2) as the metallocene. Further data were obtained with isopropylidenebis(3-tert-butyl-cyclopentadienyl)zirconium dichloride (r-Me2C(3-t-BuCp)2ZrCl2) and dimethylsilylenebisfluorenylzirconium dichloride (Me2SiFlu2ZrCl2). Main parameters of copolymerization and copolymers were determined. MAO gives rise to higher polymerization activities and lower molecular masses of the copolymers. A higher productivity is obtained with TIOAO than with TIBAO, whereas these two alumoxanes behave very similarly in determining the copolymer properties. A statistical elaboration allowed to derive the reactivity ratios of the comonomers. The copolymer microstructure is essentially due to the metallocene, even though a MAO-based catalytic system shows a slightly higher reactivity for propene.