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Activation of hafnocene catalyzed polymerization of 1-hexene with MAO and borate |
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| Authors: | Sanna Santamä ki,Esa Kokko,Markku Leskelä |
| Affiliation: | a Department of Chemistry, Laboratory of Inorganic Chemistry, University of Helsinki, P.O. Box 55, FIN 00014, Finland b Helsinki University of Technology, Department of Chemical Technology, P.O. Box 6100, FIN 02015 HUT, Finland c Borealis Polymers Oy, PO R&D, P. O. Box 330, FIN-06101 Porvoo, Finland |
| Abstract: | A study of 1-hexene polymerization with ethylene-bis(9-fluorenyl) hafnium dichloride has been carried out using two different cocatalyst systems, methyl-aluminoxane/trimethylaluminum (MAO/TMA) and tris-isobutyl-aluminum/N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate (TIBA/borate). When MAO/TMA was used, 1-hexene polymerized into a low molar mass poly(1-hexene) with low catalytic activity. Activation with TIBA/borate increased polymerization activity drastically as well as the molar mass of the polymers. In order to analyze differences in the activity profiles, UV-Vis spectroscopy was employed to investigate ligand to metal charge transitions (LMCT) of the hafnocene dichloride during the activation process. The low catalytic activity and the fast chain transfer to the cocatalyst with MAO/TMA may originate from strong bonding between the metallocene cation and the MAO/TMA species thus obstructing monomer coordination and insertion. |
| Keywords: | Hafnocene Polymerization 1-Hexene UV-Vis MAO (Methyl aluminum oxane) Borate |
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