Late Transition Metal Catalyzed Ethylene Polymerization And Copolymerization

Polyethylenes pervade almost every aspect of our daily life,driven by their superior mechanical properties,easy processabilities,and low cost.The annual global demand for these polymers has reached nearly 100 million metric tons.Despite their ubiquity and versatility,the non-polar nature of these materials still great restricts their wilder range of applications,owing to the limited surface properties,dyeabilities and incompatibility with other polymers.The introduction of some polar groups into the polyethylenes can greatly improve their properties.In this aspect,late transition metal catalyzed ethylene direct copolymerization with polar monomers proves to be the most efficient and promising way.But so far,the catalytic performance of late transition metal catalysts has not met the industrial requirements.The focus of this work is to address some issues associated with late transition metal catalyzed olefin polymerizations,in the hope of providing catalysts and polymers with better properties.The contents are as follows:1.?-Diimine palladium catalyzed ethylene copolymerization with vinyl ethers will lead to cationic polymerization and catalyst decomposition.In this part,we developed a system that combines palladium-catalyzed dimerization of vinyl ethers for the generation of ?,?-unsaturated acetals,and palladium-catalyzed ethylene copolymerization with a dimerization product for the generation of polar functionalized branched polyolefins.Importantly,the inserted acetal moiety can be readily converted to various functional groups through post-polymerization functionalization reactions,making this strategy even more versatile.This work provides an alternative route to prepare functionalized polyolefin materials.2.In the second part,we install a trifluoroborate potassium substituent on the?-diimine framework and investigated their properties in ethylene polymerizations Interestingly,the trifluoroborate potassium substituted nickel complexes(Nil and Ni2)showed better performances(higher activity and higher polyethylene molecular weight)than the unsubstituted analogues(Nil-A and Ni2-A).The ionic nature of trifluoroborate potassium brings strong affinity of the ?-diimine nickel complex on SiO2 support.The SiO2 supported catalysts demonstrate significantly better performances than the homogeneous analogues in ethylene polymerization,with extremely high activity(up to 6.53 × 107 g mol-1 h-1)and high thermal stability.The heterogeneous system leads to the formation of polyethylenes with high molecular weight(Mn up to one million).Moreover,efficient copolymerization of ethylene with methyl 10-undecenoate or 6-chloro-1-hexene can be achieved using supported catalysts.3.Finally,we studied the nickel complexes based on phosphine phosphonic amide ligand system.Interestingly,the nickel dibromide and the nickel allyl complexes are not active in ethylene polymerization.In contrast,the nickel phenyl chloride complexes are highly active in ethylene polymerization in the presence of sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate cocatalyst.In addition,these nickel complexes can initiate ethylene copolymerizations with polar functionalized comonomers including methyl 10-undecenoate,6-chloro-1-hexene and 5-acetoxy-1-pentene.More interestingly,these nickel complexes can oligomerize 1-hexene and 6-chloro-1-hexene.