Abstract
Novel bridged dinuclear diimine nickel and palladium complexes catalyzed the vinyl addition polymerization of norbornene at a single active site with high activity. The latter exhibited higher activity than the former. Smaller substituents around the imido group in the ligand were more favorable for increasing the activity than bulkier ones. The polynorbornenes were all noncrystalline but had shortβrange order and their glass transition temperature, T~g~, ranged from 270 to 400βΒ°C. Furthermore, the random copolymerization of norbornene and styrene was catalyzed by the bridged dinuclear diimine nickel complex with MAO (methylaluminoxane). Gel permeation chromatography (GPC), FTIR and ^1^H NMR spectroscopies, wideβangle Xβray diffraction (WAXD), and differential scanning calorimetry (DSC) indicated that the copolymers are βtrueβ copolymers. The reactivity ratios were r~styrene~β=β0.281, r~norbornene~β=β18.7. The packing density, thermostability and the glass transition temperatures of copolymers are increased relative to polystyrene. The solubility and processability of the copolymers are improved relative to polynorbornene.
The structures of bridged dinuclear diimine nickel and palladium complexes.
magnified imageThe structures of bridged dinuclear diimine nickel and palladium complexes.