Refernces
10.1016/S0022-328X(01)00780-X
The research details the preparation, characterization, and application of β-phenylalkyl substituted ansa half-sandwich dichloride complexes of titanium and zirconium as catalyst precursors for homogeneous ethylene polymerization. The experimental section delineates the synthesis of ligand precursors through salt elimination reactions to introduce β-phenylalkyl groups onto the aromatic system and a fulvene reaction for CMe2Ph substituents. The ansa half-sandwich complexes were then synthesized by reacting these ligand precursors with metal salts of titanium and zirconium. Additionally, the formation of metallacycles via reactions with butyllithium was investigated, which also serve as catalyst precursors. The complexes were characterized using NMR spectroscopy, including 1H-, 13C-, and 29Si-NMR, and the properties of the resulting polyethylene were assessed through parameters such as melting points, melting enthalpies, crystallinities, and molecular weights. The study also discusses the impact of the catalyst structure on the properties of polyethylene. Analytical techniques included differential scanning calorimetry (DSC), high-temperature gel permeation chromatography (HT-GPC), and mass spectrometry. The experiments were conducted using commercially available reagents and solvents, employing standard Schlenk techniques for handling sensitive reactions.
10.1002/ejic.200801121
The research investigates the use of O-acylated 2-phosphanylphenol derivatives as ligands in nickel-catalyzed ethylene polymerization. The ligands, including diphenylphosphinate and carboxylic esters, were synthesized and characterized by NMR and X-ray crystallography. These ligands formed highly active catalysts with Ni(1,5-cod)2, converting ethylene into linear polyethylene with vinyl and methyl end groups. The study found that the O-acyl bond in these ligands cleaves upon heating with nickel(0) precursors, forming active catalysts. The polymerization activity and selectivity were influenced by the nature of the O-acyl substituents, with bulkier groups leading to faster reactions and higher conversions. The research provides insights into the mechanism of ethylene polymerization with these ligands and highlights their potential for producing high-quality polyethylene.
10.1039/c2cc32834h
The research focuses on the synthesis and characterization of anisotropic nanoparticles of precisely branched polyethylenes, which exhibit a distinct oblate shape due to a crystalline lamella within the particle. The experiments involved the use of acyclic diene metathesis (ADMET) polymerization with Grubbs' catalyst to produce main-chain unsaturated polymers, followed by a secondary dispersion approach to form nanoparticles. Hydrogenation was then carried out to achieve a high degree of saturation, resulting in nanoparticles with controlled thermal behavior. The reactants used included methyl-branched alpha-olefin monomers and a ruthenium-based catalyst. Analyses employed to characterize the nanoparticles included differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and gel permeation chromatography (GPC). These techniques revealed the crystalline nature, size, shape, and thermal transitions of the nanoparticles, which were found to have a narrow melting and crystallization range, tunable down to nearly 100°C below the melting point of linear polyethylene.
