Direct synthesis of polyethylene thermoplastic elastomers with high molecular weight and excellent elastic recovery via a hybrid steric bulky strategy

Recently, α-diimine nickel-catalyzed ethylene chain walking polymerization has enabled the direct preparation of polyethylene thermoplastic elastomers using ethylene as a single feedstock. In this study, a series of hybrid bulky butyl-based α-diimine nickel complexes constructed with o-aryl and -diarylmethyl anilines were synthesized and employed for the ethylene polymerization. All the nickel complexes showed high activities (level of 106 g mol-1h−1) and high molecular weight (Mn up to 1230.9 kg/mol) polyethylene with high branching density (82–118/1000C) were yielded in ethylene polymerization. The polyethylene obtained by Ni1-3 showed distinguished elastic properties (SR = 72–91 %) and the sample obtained by Ni1 at 50 °C exhibited optimal elastic recovery values (91 %), which is also the best reported so far in polyethylene elastomers. Compared to the corresponding nickel complexes with symmetrical ligand substituents, the complexes with unsymmetrical substituents (hybrid) in this study facilitate the synthesis of significantly higher branched polyethylene with much better elastic recovery. The hybrid cationic nickel catalysts are also capable of catalyzing the copolymerization of ethylene with methyl 10-undecenoate.