Kasim F. Magomedov

Using new complexes of Group 4 metals with saligenin (2‐hydroxymethylphenol) ligands, it was shown that only titanium compounds activated by Al/Mg cocatalysts (Et ₂ AlCl or Et ₃ Al ₂ Cl ₃ + Bu ₂ Mg) exhibit catalytic activity in ethylene polymerization. The authors attribute the lack of activity of the Zr and Hf complexes to differences in the redox potentials of these metals, based on the assumption that the catalytically active particle contains reduced Ti(III). Traditional activators—alkylaluminoxanes, tetrakisperfluorophenylborates, and simple organoaluminum compounds (OAC)—are unable to activate these complexes. A prerequisite for catalytic activity is the presence of Mg compounds, indicating the heterometallic (Ti‐Mg) nature of the active particle. Titanium complexes catalyze the synthesis of UHMWPE with a productivity of up to 3940 kg of PE mol ⁻¹ h ⁻¹ atm ⁻¹ . UHMWPE films obtained by solventless processing with subsequent uniaxial orientation drawing have a tensile modulus up to 120 GPa and tensile strength up to 2.3 GPa, which indirectly proves the low degree of macromolecule's entanglements. Titanium complexes, stabilized with dichlorosaligenin ligand, are also capable of catalyzing the synthesis of high molecular weight ethylene‐propylene‐5‐ethylidene‐norbornene terpolymers (EPDM).

A series of novel complexes of titanium(IV) with OSSO-type ligands were synthesized. In the presence of Al/Mg activators such as {Et₂AlCl+Bu₂Mg} and {Et₃Al₂Cl₃+Bu₂Mg}, all the synthezed compounds catalyzed the polymerization of ethylene (with activity up to 2554 kg_PE mol_M^–1 h^–1 atm^–1). The otained ultrahigh-molecular-weight polyethylene (UHMWPE) samples had a molecular weight up to 7.6×10⁶ Da and exhibited high melting points (up to 143°C) and high crystallinity (up to 84%). It was demonstrated that these polymers can be processed by a solvent-free method into high-strength/high-modulus oriented films (with breaking strength up to 2.2 hPa and elastic modulus up to 127.7 hPa). The synthesized compounds further manifested themselves as efficient pre-catalysts (as indicated by their catalytic activity up to 408 kg_copolymer mol_M^–1 h^–1 atm^–1) for the preparation of ethylene–propylene copolymers with high propylene incorporation (up to 37%).

New alkoxo‐titanium(IV) complexes with diolate ligand containing additional donor oxygen atom have been synthesized from readily available and scalable precursors. The structure of complex 4 was established by X‐ray diffraction. Titanium atom adopts a distorted tetrahedral geometry formed by six oxygen atoms of ligands. The resulting complexes 3–4 are moderately or highly active in ethylene polymerization in the presence of {Et_nAlCl_3–n + Bu₂Mg} binary cocatalysts. The influence of the nature of the solvent, the organoaluminum cocatalyst and the polymerization temperature on the activity of catalytic systems, and the properties of the resulting polymers were studied. The obtained polymers are linear polyethylene of ultrahigh molecular weight (up to 5.8·10⁶ g mol⁻¹) with a broad molecular weight distribution. The polymers are suitable for the modern methods of polymer processing—the solventless solid‐state formation of super high‐strength (breaking strength up to 2.8 GPa) and high‐modulus (elastic modulus up to 140 GPa) oriented films and film tapes. The possibility of scaling up the synthesis of ultrahigh molecular weight polyethylene (UHMWPE) without a significant drop in the productivity of the catalytic system and polymer properties is shown. UHMWPE samples have been investigated by small‐angle X‐ray scattering (SAXS) methods to study the structural changes induced by solid‐state drawing of nascent reactor powders.