Fractionation and Crystallization of Isotactic Polypropylenes Prepared Using Homogenous Metallocene Catalyst Ismael AMER, Touhami MOKRAN & Albert VAN REENEN Download pdf. Keywords: Characterization; Metallocene Catalyst; Polymerization; Polypropylene. A b s t r a c t A series of polypropylenes were prepared using rac-ethylene-bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride (Et(H4Ind)2ZrCl2 (EI(4H)) as a homogeneous metallocene catalyst. The molecular weight of the polypropylene polymers was controlled using molecular hydrogen which was used as a transfer agent. To obtain materials with differing molecular weight and tacticities, polymers were fractionated with prep-TREF. Polypropylene polymers and fractions were fully characterized using various analytical techniques: differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), 13C nuclear magnetic resonance spectroscopy (13C-NMR) and high temperature gel permeation chromatography (HT-GPC). It was found that the addition of molecular hydrogen to propylene polymerizations catalyzed using EI(4H) catalyst system resulted in a reduction in polymer molecular weight and isotacticity. Furthermore, the molecular weight, the isotacticity and the degree of crystallinity of the TREF fractions increased significantly with increasing elution temperature for all samples. Also, only the ? crystal form existed in all TREF fractions of different samples. References Auriemma, F., De Rosa, C., Boscato, T. & Corradini, P. 2001. The oriented ? form of isotactic polypropylene. Macromolecules. 34(14): 4815-4826. Busico, V., Cipullo, R., Caporaso, L., Angelini, G. & Segre, A. L. 1998. C2- symmetric ansa-metallocene catalysts for propene polymerization: Stereoselectivity and enantioselectivity, Journal of Molecular Catalysis A: Chemical. 128(1-3): 53-64. Carvill, A., Tritto, I., Locatelli, P. & Sacchi, M. C. 1997. Polymer microstructure as a probe into hydrogen activation effect in ansa-zirconocene / methylaluminoxane catalyzed propene polymerizations. Macromolecules. 30(23): 7056-7062. Deukkil, P., Kim, I., Yang, H., Soo, S., Kim, B. & Chang, H. 2005. Isothermal crystallization behavior of metallocene-catalyzed isotactic polypropylene. Journal of Applied Polymer Science. 95(2): 231-237. Kioka, M., Makio, H., Mizuno, A. & Kashiwa, N. 1994. Tacticity distribution of polypropylene prepared by MgCl2-supported titanium catalyst. Polymer. 35(3): 580-583. Lin, S. & Waymouth, M. 1999. Regioirregular propene insertion in polypropenes synthesized with unbridged bis(2-aryl)indenyl zirconium dichloride catalysts: Implications on activity. Macromolecules. 32(25): 8283-8290. Lin, S., Kravchenko, R. & Waymouth, R. M. 2000. Ethylene and hydrogen effects in propylene polymerization with 2-arylindenyl zirconocenes. Journal of Molecular Catalysis A: Chemical. 158(1): 423-427. Moscardi, G., Piemontesi, F. & Resconi, L. 1999. Propene polymerization with the isospecific, highly regiospecific rac-Me2C(3-t-Bu-1-Ind)2ZrCl2/MAO catalyst. 1. Influence of hydrogen on initiation and propagation: Experimental detection and theoretical investigation of 2,1 propene insertion into the Zr-H bond. Organometallics. 18(25): 5264-5275. Soares, J. B. & Hamielec, A. E. 1996. Kinetics of propylene polymerization with a non-supported heterogeneous Ziegler-Natta catalyst - effect of hydrogen on rate of polymerization, stereoregularity, and molecular weight distribution. Polymer. 37(20): 4607-4614. Soga, K. & Shiono, T. 1997. Ziegler-Natta catalysts for olefin polymerizations. Progress in Polymer Science. 22(7): 1503-1546. Tsutsui, T., Kashiwa, N. & Mizuno, A. 1990. Effect of hydrogen on propene polymerization with ethylenebis(1-indenyl)zirconium dichloride and methylalumoxane catalyst system. Macromolecular Rapid Communications. 11(11): 565-570. Viville, P., Daoust, D., Jonas, A. M., Nysten, B., Legras, R., Dupire, M., Michel, J. & Debrasb, G. 2001. Characterization of the molecular structure of two highly isotactic polypropylenes. Polymer. 42(5): 1953-1967. Xu, J., Feng, L., Yang, S., Yang, Y. & Kong, X. 1998. Temperature rising elution fractionation of polypropylene produced by heterogeneous Ziegler Natta catalyst. European Polymer Journal. 34(3-4): 431-434.