Acta Chimica Sinica ›› 2023, Vol. 81 ›› Issue (6): 559-564.DOI: 10.6023/A23040162 Previous Articles     Next Articles

Communication

不对称α-二亚胺镍催化制备聚烯烃弹性体

王子豪a, 陈敏b,*(), 陈昶乐a,*()   

  1. a 中国科学技术大学高分子科学与工程系 合肥 230026
    b 安徽大学物质科学与信息技术研究院 合肥 230601
  • 投稿日期:2023-04-25 发布日期:2023-06-01
  • 作者简介:
    庆祝《化学学报》创刊90周年.
  • 基金资助:
    国家自然科学基金(52025031); 国家自然科学基金(U19B6001); 国家自然科学基金(U1904212)

Catalytic Synthesis of Polyolefin Elastomer Using Unsymmetrical α-Diimine Nickel Catalyst

Zihao Wanga, Min Chenb(), Changle Chena()   

  1. a Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026
    b Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601
  • Received:2023-04-25 Published:2023-06-01
  • Contact: *E-mail: changle@ustc.edu.cn; misschen@ahu.edu.cn
  • About author:
    Dedicated to the 90th anniversary of Acta Chimica Sinica.
  • Supported by:
    National Natural Science Foundation of China(52025031); National Natural Science Foundation of China(U19B6001); National Natural Science Foundation of China(U1904212)

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 unsymmetrical α-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 1.7×107 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 172×104 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%).

Key words: ethylene polymerization, catalyst design, unsymmetrical ligand, α-diimine nickel, materials property