N. I. Ivancheva

Properties of oriented film tapes prepared via solid-state processing of a nascent ultrahigh-molecular-weight polyethylene reactor powder synthesized with a postmetallocene catalyst

The correlation between the molecular mass of a nascent ultrahigh-molecular-weight polyethylene reactor powder synthesized with a postmetallocene catalyst and the specific features of plastic deformation during the orientational drawing of the material compacted and consolidated under laboratory conditions is studied. In the range 5 × 106−7 × 106, molecular mass is controlled via a change in the polymerization conditions. Under comparable conditions of orientational drawing, the highest values of strength (2.65 GPa) and the elastic modulus (100 GPa) are found for samples with M = 6.3 × 106.

Ethylene polymerization on titanium phenoxyimine complexes with different structures

The kinetics of ethylene polymerization in the presence of catalytic systems based on methylaluminoxane-activated titanium bis(phenoxyimine) complexes with different structures has been investigated in the temperature range 30–70°C. The structures of the complexes have different substituents at the imine nitrogen atom and in the phenoxy group in the ligand, which affect the activity of the system and the molecular weight of polyethylene resulting from polymerization over at least 1 h. The polymerization kinetics is most sensitive to the structure of the substituent at the imine nitrogen atom and to bulky substituents in the ortho position of the phenoxy group. The results obtained are explained. An attempt is made to classify the influence of the substituents in the ligands. Process conditions ensuring living polymerization have been found. The physicochemical properties and structural features of the polyethylenes obtained have been determined.

Specific features of ethylene polymerization on self-immobilizing catalytic systems based on titanium bis(phenoxy imine) complexes

The kinetics of ethylene polymerization on six methylalumoxane-activated self-immobilizing bis(phenoxy imine) complexes of titanium chloride with allyloxy groups in the m- and p-positions of the N-phenyl ring and with various substituents in the salicylaldehyde fragment was studied. The activity of the complexes in the temperature range 20–60°C and ethylene pressure of 0.4 MPa was evaluated.

Multicentered self-immobilized ethylene polymerization catalysts based on functionalized titanium halide salicylaldiminate complexes for the synthesis of ultra-high-molecular-weight polyethylene

Specific features of ethylene polymerization using a new group of catalytic systems based on ten methylalumoxane-activated titanium halide salicylaldiminato complexes functionalized with ω-vinylalkoxy groups and containing tert-butyl substituents in the phenoxide moiety were studied. The catalytic activity of the new group of activated complexes is strongly affected by the position of the ω-vinylalkoxy functional group and by the number and position of substituents in the phenoxide moiety. These factors determine the ratio of the homogeneous and heterogeneous steps of the polymerization as a result of the catalyst self-immobilization onto the polymer formed, and also the molecular characteristics of the polymer obtained at 20, 40, and 60°C and ethylene pressure of 0.4 MPa. The possibility and conditions of preparing ultra-high-molecular-weight polyethylene with improved morphology were revealed.

Self-immobilized catalysts for ethylene polymerization based on various phenoxyimine titanium halide complexes

The kinetic features of ethylene polymerization on ten methylalumoxane-activated self-immobilized bis(phenoxyimine) complexes of titanium chloride of various structure containing oxyallyl functional groups were studied. The catalytic activity of the systems was determined in the temperature range 20–60 °C under ethylene pressure 0.4 MPa. The positions and structures of the oxyallyl group and substituents in the phenoxy groups of the complexes substantially change the activity of the catalytic systems based on these complexes, the rate of the self-immobilization of the catalysts on the polymer, and molecular weights and molecular weight distributions of the obtained polyethylenes.

Polymerization of ethylene by SiO2-supported two-component catalytic systems containing bis(imino)pyridine and bis(imine) ligands

The polymerization of ethylene initiated by SiO2-supported two-component catalytic systems based on 2,6-bis[1-(2,4-dimethyl-6-cyclohexylphenylimino)ethyl]pyridine iron (II) chloride (I) and 1,2-bis(2-cyclohexyl-4,6-dimethylphenylimino)acenaphthene] nickel bromide (II) was studied. Methylaluminoxane was used as a cocatalyst during support. It was shown that the activity of two-component catalytic systems and the molecular mass and short-chain branching of polyethylene samples depend on the supporting procedure: simultaneous immobilization of components I and II, separate immobilization of components on the support (first I, then II, and vice versa), and the use of a mixture of components I and II immobilized separately on SiO2.