Latent bimodal polymerization of 1-hexene by a titanium-based diastereomeric catalyst containing a rac/meso-aminodiol ligand

A New titanium catalyst bearing an aminodiol ligand was synthesized as racemic (C-2), as meso, and as a diastercomeric mixture. The racemic catalyst (rac) produced isotactic polymer by enantiomorphic-site control mechanism whereas meso catalyst (meso) produced atactic oligomers. The rac and the diastercomeric catalyst (mix) produced polymers with single-site catalyst behavior at ambient temperatures. When the polymerization temperature was lowered, rac gave high molecular weight polyhexene with polydispersity value approaching close to a living system whereas the mix exhibited a latent bimodal behavior, meso produced just oligomers and did not show any change in behavior with polymerization temperature. Deliberate mixing of rac and meso produced two polyhexene fractions: high molecular weight polymer and oligomers indicating an independent behavior of the mixed catalyst.