二亚胺
位阻效应
支化(高分子化学)
乙烯
聚乙烯
催化作用
单体
化学
聚合
共聚物
高分子化学
聚合物
有机化学
作者
Weiqing Lu,Hui Wang,Weigang Fan,Shengyu Dai
出处
期刊:Inorganic Chemistry
[American Chemical Society]
日期:2022-04-27
卷期号:61 (18): 6799-6806
被引量:6
标识
DOI:10.1021/acs.inorgchem.1c03969
摘要
The branching density of polyethylene generated in the α-diimine Pd(II) system is usually very high, largely independent of simple ligand modifications with steric or electronic perturbations, or the polymerization conditions. In this study, we designed and synthesized a class of bulky hybrid α-diimine Pd(II) catalysts combining ortho-diarylmethyl and ortho-phenyl moieties to explore the relationship between the polyethylene microstructure and the spatial structure of catalysts. In ethylene polymerization, the hybrid α-diimine Pd(II) catalysts exhibited high activities (well above 105 g·mol-1·h-1) and yielded highly branched (90-110/1000C) polyethylenes with high molecular weights (up to 278.3 kg/mol). Compared with the two corresponding symmetrical ortho-diarylmethyl-based or ortho-phenyl-based Pd(II) catalysts, the hybrid catalysts generated polyethylene of significantly higher branching densities (92 vs 28-34/1000C) in marked higher activities. Similar phenomena are also observed in the copolymerization of ethylene with polar monomers. Moreover, the hybrid Pd(II) catalysts can more efficiently promote the copolymerization of ethylene with various polar monomers in comparison to the corresponding symmetrical catalysts. The more open spatial environment around the metal center by using a hybrid steric strategy was proposed to be responsible for above advantages.
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