Synthesis Of Nickel And Palladium Catalysts For Olefin Polymerization

Polyolefin is the most demanded polymer material in the market and plays a very important role in our daily life.Polyolefin including plastic,rubber and other polymer materials have a simple structure and excellent performance.However,traditional polyolefin materials are non-polar,which limits its use.Late transition metal catalysts can copolymerize ethylene with various polar monomers to obtain polar polyolefins.These polar polyolefins show good performance in terms of adhesion and dyeability.At present,China is still in a backward stage in the field of olefin polymerization and lacks the ability to prepare high value polyolefin materials.The development of new catalysts is the key to get high performance polyolefin materials.Therefore,our work is focused on the synthesis of excellent late transition metal catalysts.In this paper,we synthesized a series of nickel and palladium catalysts and studied their catalytic effects in ethylene polymerization and copolymerization.These types of catalysts exhibit high catalytic activity in ethylene polymerization,which can generate high-molecular-weight polymer and copolymerize ethylene with a series of polar monomers.By modifying the ligand structure,the catalyst can control the catalytic performance.1.Firstly,we synthesized a series of phosphine-sulfonate palladium and nickel complexes bearing various side-arm substituents.These phosphine-sulfonate palladium and nickel complexes emerged different effects in ethylene polymerization.Oxygen-based palladium and nickel complexes have the best catalytic effect in ethylene polymerization,which can lead to high activity and high polymer molecular weight.The sulfur-based palladium and nickel complexes have no activity in ethylene polymerization,and the palladium catalyst containing a sulfonyl group has a moderate effect in ethylene polymerization.The same trend has been maintained in the copolymerization of ethylene with methyl acrylate catalyzed by palladium catalysts.Oxygen-based palladium catalyst shows high activities and high polymer molecular weights in ethylene polymerization.2.Secondly,we synthesized a series of phosphine-sulfonate ligands and the corresponding nickel complexes.These ligands are specifically designed to bear systematically varied electron-donating and electron-withdrawing substituents.More importantly,these substituents are installed at different positions on the ligand framework,namely,the para-position of the phenylphosphino group(position X),and para to the arylsulfonate group of the main ligand(position Y).These nickel complexes are highly active single-component catalysts for the polymerization of ethylene.An electron-donating substituent at position X or an electron-withdrawing substituent at position Y is beneficial to the properties of these nickel catalysts.Specifically,the catalyst bearing the NMe2 substituent at position X exhibits high stability and high activity,and catalyzes the formation of polyethylene of high molecular weight.This catalyst also mediates the efficient copolymerizations of ethylene with methyl 10-undecenoate,6-chloro-1-hexene,and trimethoxyvinylsilane,generating copolymer with high molecular weights and high melting temperatures.Electronic effect can play a critical role in nickel-catalyzed ethylene polymerizations and copolymerizations.3.Finally,we synthesized a series of a-imino-ketone nickel catalysts.These nickel catalysts have a simple structure and exhibit high activity and thermal stability during ethylene polymerization,which can be very easy to synthesize.It is a single component catalyst,which can avoid the use of expensive aluminum cocatalyst compared to traditional a-diimine nickel catalysts.These nickel catalysts can catalyze the formation of polyethylene of high molecular weight.Due to its simple structure,it is easy to synthesize a dinuclear counterpart and a supported nickel catalyst.Surprisingly,the supported nickel catalyst can catalyze the formation of polyethylene of ultra high molecular weight.Compared to the homogeneous catalyst,the supported catalyst exhibits the better thermal stability at high temperatures.The supported nickel catalyst also can yield free-flowing polymer particles.