摘要
自齐格勒-纳塔催化剂被发现至今,烯烃聚合领域在催化剂的设计方面已经取得了巨大的突破,但是,催化剂的发展依然是此领域新鲜的源泉.通过催化剂的结构设计来影响烯烃聚合过程将一直是此领域前沿的科学问题.由于金属镍低廉的价格以及较高的丰度使其在烯烃聚合中具有广泛的应用前景.设计了三种具有不同位阻效应的不对称α-二亚胺镍催化剂,并探究了其在乙烯聚合过程中的催化性能.研究发现,催化剂的种类以及聚合条件的变化对于乙烯聚合活性,所制备聚乙烯的分子量、支化度、热力学参数以及力学性能都具有重要的影响.其中大位阻的催化剂Ni3所催化制备的聚烯烃为超高分子量聚乙烯,并同时保持了优良的力学性能以及弹性性能.
Since the discovery of Ziegler-Natta catalyst,great breakthrough has been made in the design of catalyst in olefin polymerization field,but the development of catalyst is still the fresh source in this field.It will always be a frontier scientific problem in this field to influence the olefin polymerization process through the structural design of catalysts.Due to the low cost of nickel and its high abundance,nickel-based catalysts have shown great prospects in the application of olefin polymerization.In this work,three kinds of unsymmetricalα-diimine nickel catalysts with different steric effects were designed,and their catalytic performances in ethylene polymerization were explored.It is found that the variety of catalysts and the change of polymerization conditions have important effects on the catalytic activity of ethylene polymerization,the molecular weight,branching density,thermodynamic parameters and mechanical properties of the prepared polyethylene.Among them,the polyolefin prepared by Ni3 catalyst with large steric hindrance is ultra-high molecular weight polyethylene,and the above materials maintain excellent mechanical properties and elastic properties at the same time.Specifically,tert-butyl substituted ketoimine intermediate B was condensed with three different anilines to synthesize ligands L1~L3 with different steric effects.The catalysts Ni1~Ni3 were successfully synthesized by efficient coordination reaction between the obtained ligands and DMENiBr2,and the yields were over 90%.The single crystal structures of catalysts Ni1 and Ni3 were also prepared,and the steric hindrance around the nickel center was quantified utilizing the steric maps[Vbur(Ni1)=46.1%,Vbur(Ni3)=48.7%].Under 0.8 MPa pressure of ethylene and AlEt2Cl as cocatalyst,the ethylene polymerization performance was explored using three nickel catalysts at different temperatures.Among them,Ni2 exhibited the best catalytic activity in ethylene polymerization at 50℃(up to 1.7×10^(7) g·mol^(-1)·h^(-1)),generating polyethylene with higher branching density.The polyethylene prepared by Ni3 with large steric hindrance is ultra-high molecular weight polyethylene with a molecular weight of 172×10^(4)g·mol^(-1).Moreover,polyethylene materials prepared by Ni3 also showed excellent mechanical properties(breaking stress,6~8 MPa;elongation at break,≈600%)and elastic properties(strain recovery value up to 68%).
作者
王子豪
陈敏
陈昶乐
Wang Zihao;Chen Min;Chen Changle(Department of Polymer Science and Engineering,University of Science and Technology of China,Hefei 230026;Institutes of Physical Science and Information Technology,Anhui University,Hefei 230601)
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2023年第6期559-564,共6页
Acta Chimica Sinica
基金
国家自然科学基金(Nos.52025031,U19B6001,U1904212)资助.
关键词
乙烯聚合
催化剂设计
不对称配体
α-二亚胺镍
材料性能
ethylene polymerization
catalyst design
unsymmetrical ligand
α-diimine nickel
materials property
