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. 2024 Sep 16;2(10):553-558.
doi: 10.1021/prechem.4c00057. eCollection 2024 Oct 28.

Synthesis of Ultralow-Density Polyethylene Elastomers Using Triarylnaphthyl Iminopyridyl Ni(II) Catalysts

Wenbin Yuan  1   2 , Shengyu Dai  1
Affiliations

Synthesis of Ultralow-Density Polyethylene Elastomers Using Triarylnaphthyl Iminopyridyl Ni(II) Catalysts

Wenbin Yuan et al. Precis Chem. .

Abstract

Recently, the chain-walking ethylene polymerization strategy has garnered widespread attention as an efficient and straightforward method for preparing polyolefin elastomers. In this study, a series of 2,4,8-triarylnaphthyl iminopyridyl nickel catalysts were synthesized and used in ethylene polymerization. These catalysts demonstrated moderate catalytic activity (105 g mol-1 h-1), producing high-molecular-weight (up to 145.5 kg/mol) polyethylene materials with high branching degrees (75-95/1000C) and correspondingly low melting points. Detailed analysis using 13C NMR spectroscopy revealed that the polyethylenes primarily featured methyl and long-chain branches. Mechanical testing of the polyethylene samples obtained from catalysts Ni1-Ni3 exhibited moderate stress at break (4.64-6.97 MPa) coupled with a very high strain at break (1650-3752%), indicating their very good ductility. Furthermore, these polyethylenes showcased great elastic recovery abilities, with strain recovery values ranging from 72% to 85%. In contrast, the polyethylene produced by Ni4 displayed notably inferior tensile strength (0.16 MPa) and tensile recovery (43%). To the best of our knowledge, this study represents the inaugural utilization of a nickel iminopyridyl catalyst in the preparation of a polyethylene thermoplastic elastomer.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Chart 1
Chart 1. Previously Reported Bulky α-Diimine Catalysts (A–H) for the Synthesis of POEs with High Strain Recovery and Our Current Work (I)
Scheme 1
Scheme 1. Synthesis of 2,4,8-Triarylnaphthyl Iminopyridyl Ni(II) Complexes
Figure 1
Figure 1
Plots of yield (a), molecular weight (b), and branching density (c) of the polyethylene obtained versus temperature with Ni1–Ni4.
Figure 2
Figure 2
Stress–strain curves for polyethylenes generated with (a–d) Ni1–Ni4 at 30 °C.
Figure 3
Figure 3
Plots of hysteresis experiments of ten cycles at 300% strain for polyethylenes generated by Ni1–Ni4 at 30 °C (a–d).
Figure 4
Figure 4
Detailed analysis of 1H (a) and 13C (b) NMR spectrum of the polyethylene elastomer from Table 1, entry 7. Assignments are numbered according to refs−.
Figure 5
Figure 5
Comparison of polyethylene molecular weight and branching density produced by representative reported catalysts RC-1–4 and Ni1.
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