Hu Xiaoqiang, Kang Xiaohui, Jian Zhongbao
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun, 130022, China.
University of Science and Technology of China, Hefei, 230026, China.
Angew Chem Int Ed Engl. 2022 Aug 15;61(33):e202207363. doi: 10.1002/anie.202207363. Epub 2022 Jul 4.
Living polymerization by suppressing chain transfer is a very useful method for achieving precise molecular weight and structure control. However, the suppression of chain transfer at high temperatures is extremely challenging in any catalytic polymerization. This has been a severe limitation for catalytic olefin polymerization, which is one of the most important chemical reactions. Here, we report the unprecedented living polymerization of ethylene at 130 °C, with a narrow molecular weight distribution range of 1.04 to 1.08. This is a significant increase in the reaction temperature. Tailor-made α-diimine nickel catalysts that exhibit both the steric shielding and fluorine effects play an essential role in this breakthrough. These nickel catalysts are even active at 200 °C, and enable the formation of semi-crystalline, ultrahigh-molecular-weight polyethylene at 150 °C. Mechanistic insights into the key chain transfer reaction are elucidated by density functional theory calculations.
通过抑制链转移实现的活性聚合是实现精确分子量和结构控制的非常有用的方法。然而，在任何催化聚合反应中，在高温下抑制链转移都极具挑战性。这一直是催化烯烃聚合反应（最重要的化学反应之一）的严重限制。在此，我们报道了在130°C下实现的前所未有的乙烯活性聚合，分子量分布范围狭窄，为1.04至1.08。这是反应温度的显著提高。兼具空间位阻屏蔽和氟效应的定制α-二亚胺镍催化剂在这一突破中起着至关重要的作用。这些镍催化剂在200°C时仍具有活性，并能在150°C下形成半结晶的超高分子量聚乙烯。通过密度泛函理论计算阐明了关键链转移反应的机理。
