Acta Chimica Sinica ›› 2022, Vol. 80 ›› Issue (6): 741-747.DOI: 10.6023/A22020066 Previous Articles     Next Articles

Special Issue: 有机氟化学合集

Article

空间位阻与氟效应协同增强镍系乙烯聚合

王玉银a,b,c, 胡小强c, 穆红亮c, 夏艳a,*(), 迟悦b,*(), 简忠保c,*()   

  1. a 长春工业大学 化学与生命科学学院 高等材料研究院 长春 130012
    b 长春工业大学 材料科学与工程学院 先进结构材料教育部重点实验室 长春 130012
    c 中国科学院长春应用化学研究所 高分子物理与化学国家重点实验室 长春 130022
  • 投稿日期:2022-02-10 发布日期:2022-07-07
  • 通讯作者: 夏艳, 迟悦, 简忠保
  • 基金资助:
    国家自然科学基金(22122110); 吉林省教育厅(JJKH20210728KJ)

Enhancement on Nickel-Mediated Ethylene Polymerization by Concerted Steric Hindrance and Fluorine Effect

Yuyin Wanga,b,c, Xiaoqiang Huc, Hongliang Muc, Yan Xiaa(), Yue Chib(), Zhongbao Jianc()   

  1. a College of Chemistry and Life Science, Advanced Institute of Materials Science, Changchun University of Technology, Changchun 130012
    b Key Laboratory of Advanced Structural Materials of Ministry of Education, College of Material Science and Engineering, Changchun University of Technology, Changchun 130012
    c State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022
  • Received:2022-02-10 Published:2022-07-07
  • Contact: Yan Xia, Yue Chi, Zhongbao Jian
  • Supported by:
    National Natural Science Foundation of China(22122110); Education Department of Jilin Province(JJKH20210728KJ)

Olefin polymerization is one of the most important chemical reactions in industry. Transition metal catalysts are the key to the development of olefin polymerization. Neutral salicylaldiminato nickel catalyst stands out due to the nature of both functional-group tolerance and cocatalyst-free. Either sterically hindered effect or fluorine effect has extensively been reported over the past decades to improve properties of neutral and single-component salicylaldiminato nickel catalyst; however, combination of these two effects to generate a concerted strategy is much less studied. In this work, both para-sterically hindered substituents including phenyl, 1-naphthyl or 9-anthracenyl group and ortho-fluorine substituents are concurrently installed into salicylaldimine ligands, and thus five salicylaldiminato nickel catalysts have been synthesized and fully identified by 1H and 13C NMR spectroscopy, elemental analysis and X-ray diffraction technique if possible. Without the addition of any activator, these single-component nickel catalysts are used to ethylene polymerization. Influence of sterically hindered effect, fluorine effect, reaction temperature and reaction time on catalytic activity, polymer molecular weight, and branching density of polymer is comprehensively investigated. ortho-Fluorine substituents particularly elevate catalytic activity, lifetime of catalyst species, and polymer molecular weight, while decreases branching density of polymer. Enhancement of catalytic activity and polymer molecular weight reaches two orders of magnitude and 36 times, respectively; and linear structure (5 branches/1000 carbon) of polyethylene can be accessible. This should originate from the inhibition of both chain transfer and chain walking pathways. The bulk of para-sterically hindered substituents can be designed according to the required catalytic activity and molecular weight, and notably it has a minor influence on branching density of polymer. The concerted combination of fluorine effect and steric shielding effect enables the formation of linear ultrahigh molecular weight polyethylene (UHMWPE). This work develops a new strategy for the efficient design of salicylaldiminato nickel olefin polymerization catalyst.

Key words: olefin polymerization, fluorine effect, steric hindrance, nickel catalyst, salicylaldimine