Defined synthesis of copolymers using metallocene catalysis

Abstract

The copolymerization of propene with small amounts of ethene, catalyzed by tetrahydroindenyl zirconocenes such as [En(H 4 Ind) 2 ]ZrCl 2 or [Me 2 Si(H 4 Ind) 2 ]ZrCl 2 and MAO in liquid propene produces polymers with much higher activities and molecular weights than the homopolymerization of propene. The normal bisindenyl complexes doesn't present such differences. The investigation of the microstructure shows for the tetrahydroindenyl catalyst that after a 2,1-insertion of a propene unit the system is in a sleeping state and can be activated when an ethene unit is inserted. In this case these catalysts become faster than the ansa bis-indenyl catalysts. An active catalyst for the copolymerization of ethene and norbornene is the more temperature stable [Me3PhPen(Flu)]ZrCl2. This catalyst produces atactic copolymers with high molecular weights of over 900 000 g/mol at 30 °C and 38 mol % of norbornene content.