Star Ultrahigh-Molecular-Weight Polyethylene

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.