This work reports a facile and versatile ring-opening metathesis polymerization of three- and four-armed star-shaped poly(ε-caprolactone) (PCL) macromonomers bearing a norbornenyl group at each chain end using Grubbs’ third-generation catalyst under diluted condition to obtain graft polymers (GPs) comprising densely arrayed three- and four-armed cage-shaped grafted PCLs (GPCLs) with narrow dispersity (1.19–1.35) and a controllable number of cage repeating units up to 40 (molecular weight: ∼320 000 g mol^–1). The GPCLs were characterized using nuclear magnetic resonance spectroscopy, size exclusion chromatography, and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. The cyclopolymerization proceeded via repetitive rapid intramolecular reactions to form cage-shaped units followed by slow intermolecular propagation. This synthesis was applicable to star-shaped poly(l-lactide), poly(trimethylene carbonate), and poly(ethylene glycol). Investigating the structure–property relationships regarding crystallization behavior, hydrodynamic diameter, and viscosity revealed that cage-shaped topological side chains reduced the chain dimensions and mobility compared to their linear and cyclic counterparts.

中文翻译：

---

通过星形大分子单体的环聚合合成密集排列的笼形聚合物拓扑结构

这项工作报告了在稀释条件下使用 Grubbs 的第三代催化剂在每个链端带有降冰片烯基的三臂和四臂星形聚（ε-己内酯）（PCL）大分子单体的简便且通用的开环复分解聚合反应获得包含密集排列的三臂和四臂笼状接枝 PCL (GPCL) 的接枝聚合物 (GP)，具有窄分散性 (1.19–1.35) 和可控数量的笼重复单元，最多 40 个（分子量：~320 000克摩尔^–1）。使用核磁共振光谱、尺寸排阻色谱和基质辅助激光解吸/电离飞行时间质谱对 GPCL 进行表征。环聚合通过重复的快速分子内反应进行，形成笼状单元，然后缓慢分子间传播。该合成适用于星形聚（l-丙交酯）、聚（三亚甲基碳酸酯）和聚（乙二醇）。研究关于结晶行为、流体动力学直径和粘度的结构-性质关系表明，与线性和环状对应物相比，笼形拓扑侧链降低了链的尺寸和流动性。