Direct Synthesis of Polyethylene Thermoplastic Elastomers Using Hybrid Bulky Acenaphthene-Based α-Diimine Ni(II)...

Recently, polyolefin thermoplastic elastomers can be obtained directly using ethylene as a single feedstock via α-diimine nickel-catalyzed ethylene chain walking polymerization. Here, a new range of bulky acenaphthene-based α-diimine nickel complexes with hybrid o-phenyl and -diarylmethyl anilines were constructed and applied to ethylene polymerization. All the nickel complexes under the activation of excess Et₂AlCl exhibited good activity (level of 10⁶ g mol^-1 h^-1) and produced polyethylene with high molecular weight (75.6-352.4 kg/mol) as well as proper branching densities (55-77/1000C). All the branched polyethylenes obtained exhibited high strain (704-1097%) and moderate to high stress (7-25 MPa) at break values. Most interestingly, the polyethylene produced by the methoxy-substituted nickel complex exhibited significantly lower molecular weights and branching densities, as well as significantly poorer strain recovery values (48% vs. 78-80%) than those by the other two complexes under the same conditions.