The existing catalyst/initiator systems and methodologies used for the synthesis of polymers can access only a few cyclic polymers composed entirely of a single monomer type, and the synthesis of such authentic cyclic polar vinyl polymers (acrylics) devoid of any foreign motifs remains a challenge. Here we report that a tethered B-P-B trifunctional, intramolecular frustrated Lewis pair catalyst enables the synthesis of an authentic cyclic acrylic polymer, cyclic poly(γ-methyl-α-methylene-γ-butyrolactone) (c-PMMBL), from the bio-based monomer MMBL. Detailed studies have revealed an initiation and propagation mechanism through pairwise monomer enchainment enabled by the cooperative and synergistic initiator/catalyst sites of the trifunctional catalyst. We propose that macrocyclic intermediates and transition states comprising two catalyst molecules are involved in the catalyst-regulated ring expansion and eventual cyclization, forming authentic c-PMMBL rings and concurrently regenerating the catalyst. The cyclic topology of the c-PMMBL polymers imparts an ~50 °C higher onset decomposition temperature and a much narrower degradation window compared with their linear counterparts of similar molecular weight and dispersity, while maintaining high chemical recyclability.

现有的用于聚合物合成的催化剂/引发剂系统和方法只能获得少数完全由单一单体类型组成的环状聚合物，而合成这种不含任何外来基序的真实环状极性乙烯基聚合物（丙烯酸）仍然是一个挑战. 在这里，我们报告了一种系链 BPB 三功能分子内受挫路易斯对催化剂能够从生物基合成真正的环状丙烯酸聚合物，环状聚（γ-甲基-α-亚甲基-γ-丁内酯）（c-PMMBL）单体MMBL。详细的研究揭示了通过三功能催化剂的协同和协同引发剂/催化剂位点实现的成对单体链的引发和传播机制。我们提出包含两个催化剂分子的大环中间体和过渡态参与催化剂调节的环膨胀和最终环化，形成真正的 c-PMMBL 环并同时再生催化剂。与具有相似分子量和分散性的线性对应物相比，c-PMMBL 聚合物的环状拓扑结构使其起始分解温度高约 50 °C，降解窗口更窄，同时保持较高的化学可回收性。