Schiff-base nickel nanoparticlesNanoparticle-assisted polymerizationalpha-olefin co-oligomerizationStyrene coordination polymerizationSTYRENE POLYMERIZATIONSYNDIOSPECIFIC POLYMERIZATIONSYNDIOTACTIC POLYSTYRENEETHYLENE POLYMERIZATIONSTERIC HINDRANCEALPHA-OLEFINSNICKELMETHYLALUMINOXANECOPOLYMERIZATIONMECHANISM