Appreciable norbornene incorporation in the copolymerization of ethyleneorbornene using titanium catalysts containing trianionic N[CH2CH(Ph)O](3)(3-) ligands

摘要

The newly synthesized 1-TiCl (C-3 symmetric) and 2-TiCl (C-s symmetric) precatalysts in combination with MAO polymerized ethylene, cyclic olefins, and copolymerized ethyleneorbornene in good yields. The catalyst with C-3 symmetry exhibits moderate catalytic activity and efficient norbornene incorporation for E/NBE copolymerization in the presence of MAO [activity = 360 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL, 10 min], affording poly(ethylene-co-NBE)s with high norbornene contents (42.0%) and the C-s symmetric catalyst showed an activity of 420 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL affording poly(ethylene-co-NBE)s with 33.0% norbornene content. The effect of monomer concentration at ambient temperature and constant Al/Ti ratio for the homo and copolymerization was studied in a detailed manner. We found that apart from the electronic environment around the metal center the steric environment provided by the symmetry of the catalyst systems has a considerable influence on the percentage of norbornene content of the copolymer obtained. We also found that with a given catalyst a variable clearly influencing the copolymer microstructure, hence also the copolymer properties, is the monomer concentration at a given feed ratio. (C) 2007 Wiley Periodicals, Inc.