Late transition metal-catalyzed ethylene chain-walking polymerization offers a remarkably convenient method for synthesizing hyperbranched polyethylene. In this study, we created a series of pyridine-imine Ni(II) complexes with axially flexible cycloalkyl substituents, tailored for the production of hyperbranched oligoethylene oils (HBOEOs). These complexes exhibited moderate activity in HBOEO synthesis, reaching rates of up to 4.90 × 10⁵ g mol⁻¹ h⁻¹. The resulting products exhibited low molecular weights (325–523 g mol⁻¹) and high branching densities (110–167/1000C). NMR analysis verified their diverse branching structures, with a significant proportion of hyperbranched motifs. Notably, the activity, structure, and properties of the HBOEOs produced by the catalytic system were significantly influenced by alterations in the catalyst structure and oligomerization conditions. Specifically, when compared to rigid phenyl substituents, flexible cycloalkyl substituents proved more effective in promoting the catalytic system to produce HBOEOs with a higher degree of branching and improved liquefaction properties.

中文翻译：

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镍催化直接合成超支化液体低聚乙烯


晚期过渡金属催化的乙烯链步聚合为合成超支化聚乙烯提供了一种非常方便的方法。在这项研究中，我们创建了一系列具有轴向柔性环烷基取代基的吡啶-亚胺 Ni（II） 配合物，专为生产超支化寡乙烯油 （HBOEO） 量身定制。这些复合物在 HBOEO 合成中表现出中等活性，速率高达 4.90 × 10⁵ g ^{mol-1 h-1}。所得产物表现出低分子量 （325-523 g ^mol-1） 和高支化密度 （110-167/1000C）。NMR 分析验证了它们多样化的分支结构，其中很大一部分是超分支基序。值得注意的是，催化体系产生的 HBOEO 的活性、结构和性质受到催化剂结构和低聚化条件改变的显著影响。具体来说，与刚性苯基取代基相比，柔性环烷基取代基被证明在促进催化系统产生具有更高支化程度和改善液化性能的 HBOEO 方面更有效。