A disubstituted-norbornene-based comonomer strategy to address polar monomer problem

• 作者: Menghe Xu Changle Chen
• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2021,（14）
• 所属期刊栏目: ARTICLES
• 页码范围: 1429-1436
• 页数: 8页
• 语种: 英文

摘要

The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar groups towards Lewis acidic metal centers and the drastic reactivity differences of polar comono-mers versus non-polar olefins,it is challenging to develop catalysts that provide the desired polymer molecular weight,comonomer incorporation,and activity.In this contribution,we tackle this issue from a comonomer perspective using 5,6-disubstituted norbornenes,which are highly versatile,easily acces-sible,inexpensive,and capable of introducing two functional groups in a single insertion.More impor-tantly,they are only mildly poisoning due to the presence of long spacers between double bonds and polar groups,and are not prone to p-hydride elimination due to their cyclic structures.As strong n-donors,they can competitively bind to metal centers versus olefins.Indeed,phosphine-sulfonate palla-dium catalysts can catalyze the copolymerization of ethylene with 5,6-disubstituted norbornenes and simultaneously achieve a high polymerization activity,copolymer molecular weight,and comonomer incorporation.The practicality of this system was demonstrated by studying the properties of the result-ing polymers,copolymerization in hydrocarbon solvents or in bulk,recovery/utilization of unreacted comonomer,molecular weight modulation,and large-scale synthesis.