Synthesis of MWNTs/SiO2 supported nickel and palladium complexes and their application as catalysts for cyclic olefins polymerization

Abstract

Nickel and palladium complexes bearing hydroxyl‑functionalized ligand {C10H8(O)C[4-C6H4(C2H4OH)NH]CH3} were synthesized, and supported on trimethylaluminum (Me3Al) activated nano-silica (SiO2) or multiwalled carbon nanotubes (MWNTs). The molecular structures of the complexes have been confirmed by NMR and XPS. The effects of homogeneous nickel and palladium catalysts as well as MWNTs/SiO2 supported nickel and palladium catalysts on the polymerization of norbornene (NB) were systematically investigated. MWNTs covalently immobilized bonded catalysts had the highest activity (3.27 × 104 gpolymer molNi−1h − 1) and yield (98.2%) in copolymerization for norbornene (NB) with 5-norbornene-2-carboxylic ester (NB-COOCH3). The NB-COOCH3 insertion ratio of the obtained copolymer could reach up 40.82% when the NB-COOCH3 feed ratio was 50%. The vinyl-addition polynorbornene nanocomposites exhibited high thermal stability (Td > 400 °C) and good solubility. The SEM and TEM images of polynorbornene showed that nano-particles were dispersed uniformly in polymers. The processability and mechanical properties of the obtained copolymers were improved effectively.