First report of Schiff-base nickel nanoparticle-catalyzed oligomerization and polymerization of norbornene

Ten novel Schiff-base functionalized nickel nano-systems were synthesized to investigate the capping ability of the ligands as well as the stability of the resulting nanoparticles. All four ligands employed were found to be capable and comparable stabilizers to produce monodispersed nanoparticles. These nanoparticles were further evaluated as catalysts in the polymerization of norbornene, using MAO or MMAO as a co-catalyst. All ten nanomaterials were active polymerization catalysts, resulting in the first ever reported nanoparticle-assisted polymerization processes. It was shown that the nano-catalyst can facilitate either oligomerization or polymerization depending on the co-catalyst employed. Other than vinyl polynorbornene, hydroxy functionalized oligomer stabilized nanocomposite products were also obtained. The oligomers could be cleaved from the nanoparticle surface, depending on its intended application. The vinyl polymers obtained gave high molecular weights and low polydispersity indices, whereas the hydroxy oligomers gave low molecular weight oligomers that were monodispersed. It was shown that the metal to ligand concentration, i.e. the extent of the nanoparticle surface stabilization, has little influence on the catalytic activity but rather influenced the polymer selectivity. A higher ligand to metal ratio resulted in higher molecular weight polymers with lower polydispersity indices compared to the lower metal to ligand ratio analogues. The effect of the type of ligand employed, is also investigated. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

Ten novel Schiff-base functionalized nickel nano-systems were synthesized and evaluated as catalysts in polymerization reactions. The nanoparticles exhibited good stability and activity, demonstrating diverse functionalities in polymerization processes.