支化(高分子化学)
乙烯
共聚物
聚合
高分子化学
材料科学
产品分销
聚合度
摩尔质量分布
聚合物
化学
催化作用
有机化学
复合材料
作者
Yuxing Zhang,Xiaohui Kang,Zhongbao Jian
标识
DOI:10.1038/s41467-022-28282-z
摘要
Polyolefins with branches produced by ethylene alone via chain walking are highly desired in industry. Selective branch formation from uncontrolled chain walking is a long-standing challenge to generate exclusively branched polyolefins, however. Here we report such desirable microstructures in ethylene polymerization by using sterically constrained α-diimine nickel(II)/palladium(II) catalysts at 30 °C-90 °C that fall into industrial conditions. Branched polyethylenes with exclusive branch pattern of methyl branches (99%) and notably selective branch distribution of 1,4-Me2 unit (86%) can be generated. The ultrahigh degree of branching (>200 Me/1000 C) enables the well-defined product to mimic ethylene-propylene copolymers. More interestingly, branch distribution is predictable and computable by using a simple statistical model of p(1-p)n (p: the probability of branch formation). Mechanistic insights into the branch formation including branch pattern and branch distribution by an in-depth density functional theory (DFT) calculation are elucidated.
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