Highly Active Living Random Copolymerization of Norbornene and 1-Alkene with ansa-Fluorenylamidodimethyltitanium Derivative: Substituent Effects on Fluorenyl Ligand

Abstract

Copolymerizations of norbornene with propylene and 1-octene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe2Flu]TiMe2 (1), [t-BuNSiMe2(3,6-tBu2Flu)]TiMe2 (2), [t-BuNSiMe2(2,7-tBu2Flu)]TiMe2 (3), and [t-BuNSiMe2(C29H36)]TiMe2 (4; C29H36, octamethyloctahydrodibenzofluorenyl), activated by trialkylaluminum-free modified methylaluminoxane. The catalytic systems promoted random copolymerizations in a living manner regardless of the titanium complex used. The activity increased by the introduction of the tBu groups on the Flu ligand, and 4 showed the highest activity for each copolymerization. The comonomer content of the copolymers obtained was controllable in a wide range by changing comonomer feed ratio with these catalytic systems. The linear relationships were observed between the norbornene content and the glass transition temperature of the copolymer, whereas the slopes depended on the titanium complex used. The result suggested that the titanium complexes affected the microstructures of the copolymers produced. The evaluation of the monomer reactivity ratios in the copolymerization of norbornene with 1-octene indicates a preference for the norbornene insertion regardless of the last inserted monomer unit in growing polymer chain in all the catalytic systems.