Hyperbranched macromolecules bridged salicylaldimine cobalt complexes: synthesis, characterization and ethylene oligomerization studies

Synthesis of New Dendritic Titanium Catalysts and Catalytic Ethylene Polymerization

The 1.0G dendrimer polyamidoamine (PAMAM), 3,5-dichlorosalicylaldehyde, and TiCl₄·2THF were used as synthetic materials, and the dendritic salicylaldehyde imide ligand with substituent hindrance and its titanium catalyst were synthesized by the condensation reaction of Schiff base. The structure of the synthesized products was characterized by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, ultraviolet spectroscopy, electrospray mass spectrometry, and inductively coupled plasma-mass spectrometry. Activated methylaluminoxane (MAO) was used as a catalyst precursor for ethylene polymerization in the process of ethylene catalytic. The effects of ethylene polymerization were studied in terms of the Al/Ti molar ratio, reaction time, reaction temperature, polymerization pressure, and ligand structure of the catalyst. The results show good catalytic performance (70.48 kg PE/mol Ti·h) for ethylene polymerization because of the existence of ortho substituent hindrance on the salicylaldehyde skeleton. Furthermore, high-temperature gel permeation chromatography (GPC)-IR, differential scanning calorimetry (DSC), and torque rheometer were used to characterize the microstructure, thermal properties, and viscoelastic state of the polyethylene samples obtained. The results showed that the product was ultrahigh-molecular-weight polyethylene.

Synthesis and ethylene polymerization reaction of dendritic titanium catalysts

The 1.0 G dendrimer (C₂₂H₄₈N₁₀O₄),3,5-di-tert-butylsalicylaldehyde and TiCl₄ · 2THF were used as the synthetic materials, and the dendritic salicylaldehyde imide ligand with substituent hindrance and its titanium catalyst were synthesized by the condensation reaction of schiff base. The structure of the synthesized products was characterized by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, ultraviolet spectroscopy, electrospray mass spectrometry, and inductively coupled plasma mass spectrometry, The actual structure is consistent with the theoretical design structure. Activated methylaluminoxane (MAO) was used as a catalyst precursor for ethylene polymerization in the process of ethylene catalytic. The effects of ethylene polymerization were studied in terms of the Al/Ti molar ratio, reaction time, reaction temperature, polymerization pressure, and ligand structure of the catalyst. The results show at the reaction temperature of 25°C, the reaction time was 30 min, and the ethylene pressure was 1.0 MPa and Al/Ti was 1,000, the catalytic activity can reach 78.56 kg PE/(mol Ti.h). Furthermore, high-temperature GPC-IR, DSC, and torque rheometer were used to characterized the microstructure, thermal properties, and viscoelastic state of polyethylene samples obtained. The results showed that the product was ultra-high-molecular-weight polyethylene.

Water vapor permeable polyurethane films based on the hyperbranched aminoethers of boric acid

The hyperbranched polymers have drawn intensive attention in the design of macromolecules and functional materials because of their unique physical and chemical properties resulting from the branched architecture and the high number of functional groups. In the present study, by means of light scattering, viscosimetry, thermomechanical analysis, tensile stress–strain, mechanical loss tangent and water vapor permeability measurements, we demonstrate the hierarchical macromolecular organization of organoboron polyurethanes synthesized using sterically hindered amino ethers (AEBA) of boric acid. It is shown that the water vapor permeability of polyurethanes obtained on the basis of sterically hindered aminoethers of boric acid is due to the peculiarities of the chemical structure of AEBA, which can exhibit an ionomeric nature and the presence of steric hindrances created in the hyperbranched structure of AEBA, which can lead to an increase in free volume in such polyurethanes.

It is shown that the water vapor permeability of polyurethanes obtained on the basis of sterically hindered aminoethers of boric acid is due to the peculiarities of the chemical structure of AEBA.