Isoselective Ring-opening Polymerization of Racemic Lactide Catalyzed by N-heterocyclic Olefin/(Thio)urea Organocatalysts

• 作者: Zhen-Yu Wang Guang-Qiang Xu Li Zhou Cheng-Dong Lv Ru-Lin Yang Bing-Zhe Dong Qing-Gang Wang
• 来源期刊: 高分子科学（英文版）
• 年，卷（期）: 2021,（6）
• 所属期刊栏目: ARTICLES
• 页码范围: 709-715
• 页数: 7页
• 语种: 英文

摘要

The isoselective ring-opening polymerization of racemic lactide was achieved by combining N-heterocyclic olefin (NHO) with mono(thio)ureas or bis(thio)ureas as catalytic systems.The polymerization process shows high stereoselectivity,controllability and reactivity,delivering multi-block isotactic polylactides with high chain-end fidelity and narrow molecular weight distributions.The enhancement of catalytic performance was observed in the following order: bisthiourea (DTU) ＜ monothiourea (TU) ＜ bisurea (DU) ＜ urea (U).The highest Pm (probability of forming a meso dyad) =0.91 was observed at-70 ℃ when using NHO/U1 catalytic system and the high stereoselectivity was attributed to chain-end control mechanism.