Star Ultrahigh-Molecular-Weight Polyethylene
Chaoqun Wang, Shilong Wu, Quan Chen, Hongliang Mu, Zhongbao Jian
Abstract
Star polymers have attracted immense interest from scientific and industrial communities due to their unique properties relative to linear polymers; however, the synthesis of the long-sought star polyolefins remains highly challenging because of the lack of desired catalysts. Herein, we report the synthesis of tri- and tetranuclear neutral salicylaldiminato nickel(II) catalysts through well-defined multinuclear nickel(II) precursors rather than multisite ligands. A one-step and clean synthesis of three-arm and four-arm star polyethylenes without tedious purification via the core-first approach is accomplished by these nickel(II) catalysts. These star polyethylenes possess ultrahigh molecular weights of 1432–2370 kDa, very narrow molecular weight distributions of M w / M n = 1.30–1.39, substantially linear arms of 1.7–3.0 branches/1000C, and excellent mechanical properties. As a result, star ultrahigh-molecular-weight polyethylene has become a new member of the family of polyolefins.