A series of unsymmetrical 1-[2,6-bis(bis(4-fluorophenyl)methyl)-4-MeOC6H2N]-2-aryliminoacenaphthene-nickel(II) halides has been synthesized and fully characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (H-1 NMR), C-13 NMR, and F-19 NMR spectroscopy as well as elemental analysis. The structures of Ni1 and Ni6 have been confirmed by the single-crystal X-ray diffraction. On activation with cocatalysts either ethylaluminum sesquichloride or methylaluminoxane, all the title nickel complexes display high activities toward ethylene polymerization up to 16.14 x 10(6) g polyethylene (PE) mol(-1)(Ni) h(-1) at 30 degrees C, affording PEs with both high branches (up to 103 branches/1000 carbons) and molecular weight (1.12 x 10(6) g mol(-1)) as well as narrow molecular weight distribution. High branching content of PE can be confirmed by high temperature C-13 NMR spectroscopy and differential scanning calorimetry. In addition, the PE exhibited remarkable property of thermoplastic elastomers (TPEs) with high tensile strength (sigma(b) = 21.7 MPa) and elongation at break (epsilon(b) = 937%) as well as elastic recovery (up to 85%), indicating a better alternative to commercial TPEs. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 130-145