نتایج جستجو برای: dual site ethylene polymerization catalysts
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Linear aliphatic polyesters are degradable thermoplastic polymers, which can be obtained by ring-opening polymerization (ROP) of cyclic esters through a coordination-insertion mechanism. Aluminum based organometallic complexes have a leading position as efficient catalysts for this polymerization process. Aluminumalkyl complexes bearing salicylaldiminato ligands, although less explored, have be...
More than 70 million tons of polyethylene and polypropylene are produced annually. The majority is prepared by catalytic polymerization employing Ziegler or Phillips catalysts based on early transition metals. More recently, olefin polymerization by complexes of late transition metals has also received increasing attention. A major motivation is their higher tolerance towards polar reagents due...
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The interaction of the external donor (propyltrimethoxysilane - PTMS) with titanium-magnesium catalysts (TMCs) containing dibutylphthalate (DBP) as internal donor, which were prepared in different ways, was studied by chemical analysis and infrared diffuse reflectance spectroscopy (DRIFTS). The chemical composition of the catalysts after their interaction with heptane solutions of PTMS, PTMS/Al...
Organic superbases reacted with alkyl iodides (R–I) to reversibly generate the corresponding alkyl radicals (R). Via this reaction, organic superbases were utilized as new and highly efficient organic catalysts in living radical polymerization. The superbase catalysts included guanidines, aminophosphines and phosphazenes. Low-polydispersity polymers (Mw/Mn = 1.1–1.4) were obtained up to high co...
It is a long-standing challenge to combine mixed monomers into multiblock copolymer (MBC) in a onepot/one-step polymerization manner. We report the first example of MBC with biodegradable polycarbonate and polyester blocks that were synthesized from highly efficient one-pot/one-step polymerization of cyclohexene oxide (CHO), CO2 and 3-caprolactone (3-CL) in the presence of zinc– cobalt double m...
Porous organic polymers (POPs) are widely used in various areas such as adsorption, separation and catalysis. In the present work, ionic liquid-modified porous (IL-POPs) synthesized by dispersion polymerization were applied to immobilize metallocene catalysts for olefin polymerization. The prepared IL-POPs characterized Fourier transform infrared spectrometer (FT-IR), nitrogen sorption porosime...
Developing selective polymerizations from complex monomer mixtures is an important challenge. Here, dinuclear catalysts allow selective polymerization from mixtures of sterically hindered tricyclic anhydrides, carbon dioxide and epoxides to yield well-controlled copoly(ester-carbonates). Surprisingly, two very similar homogeneous catalysts differing only in the central metal, zinc versus magnes...
Polyesters, especially poly(lactide) (PLA), are used widely as biodegradable and biocompatible materials, yet their controllable synthesis, especially the stereoselective synthesis of polyesters, is still a challenge. Recently some excellent Lewis pair catalysts for ring-opening polymerization (ROP) of lactide and related cyclic esters have emerged. This review article will highlight the key ad...
Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing six-car...
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