Constrained Geometry Metallocene Catalyst: Synthesis, Characterization And Catalytic Performance For Olefin Polymerization

Olefin coordinating polymerization catalyst has become an important branch of thepolymer chemistry area, and it is also the basis of the development of polyolefinindustry. Not only the metallocene catalysts are occupying more and more marketshare for its superior catalytic properties, but also the designation of the catalyst andperformance of the polymer greatly enriched the connotation of polymer chemistryand other disciplines. Beyond all doubt, the prospect of metallocene catalysts is veryoptimistic. As a branch of the metallocene catalysts, the constrained geometrymetallocene catalysts can produce an unique and high processing performancepolymer having a narrow molecular weight distribution and long chain branches.Metallocene catalysts can synthesize a series of high performance polymerizationproducts, such as isotactic polypropylene, syndiotactic polypropylene, syndiotacticpolystyrene, low density polyethylene, high density polyethylene and the cyclic olefincopolymer, etc.. Depending on these advantages in the synthesis of polymerizationproducts from metallocene catalysts, we need to continue to improve the effect ofsubstituents on the metallocene catalysts for olefin polymerization. Therefore, weexpect to further optimize the structures of the catalysts and the polymerizationconditions to synthesize a more excellent performance polyolefin products.In this paper, we designed and synthesized four excellent single-metallocene structure ligands L1-L4, characterizing their structures by elements analysis,1H NMRand13C NMR. Reacting with TiCl4through these ligands or their lithium salt at lowtemperature, we synthesized three constrained geometry metallocene complexesCat.1-Cat.4, and their structures were confirmed by elemental analysis,1H NMR,13CNMR and crystallography diffraction. We also studied the catalytic properties aboutethylene polymerization and ethylene/1-hexene copolymerization upon activationwith AlR3and Ph3CB(C6F5)4of the three complexes. Compared with thepolymerization results under known structure of the catalyst before in the sameconditions, we found that there have a more significant improvement in terms ofactivity, molecular weight, total monomer content of the polymer.