Olefin Polymerization Behavior of Titanium(IV) Complexes with Fluorinated and Non-fluorinated Aliphatic Phenoxyimine Ligands

A series of Ti(IV) dichloride and dialkoxide complexes with phenoxyimine ligands containing fluorinated and nonfluorinated aliphatic imine fragments have been synthesized. The molecular structures of complexes 1 and 4 were established by single-crystal X-ray diffraction studies. The complexes adopt a distorted octahedral coordination structure around the titanium atom and two oxygen atoms are situated in trans position while two nitrogen atoms and two outgoing ligands (Cl or i PrO) are situated in cis position. Effect of activators (MMAO-12 and combinations Et n AlCl 3− n + Bu 2 Mg) and outgoing ligand (Cl or i PrO) nature on the catalytic activity and properties of the resulting polymers was studied. The Ti complexes, despite the nature of the outgoing ligands (Cl or i PrO) in the presence of Al/Mg activators, was found to display a high ethylene polymerization activity in the range 1600–3830 kg polymer ·mol Ti −1 ·h −1 ·atm −1 with a viscosity average molecular weight ( M v ) value in the range 1.1×10 6 −7.1×10 6 Dalton (Da). The resulting UHMWPE can be processed by a solventless method into high-strength and high-modulus oriented films. The rheological characteristics of a polymer melt have been studied. The absence of a cross-over point did not allow to compare the values of the molecular weight distribution of polymers obtained on fluorinated and non-fluorinated pre-catalysts, however, the estimation of the entanglement density is in good agreement with the mechanical characteristics of oriented films. Upon activation with methylalumoxane, the activity of the complexes decreased very significantly; however, a polymer with a molecular weight of about 12 million Da was obtained. In the process of ethylene/octene-1 copolymerization, fluorine-containing precatalysts showed a clear advantage over non-fluorinated analogues both in activity and in comonomer content.