美国科罗拉多州立大学Eugene Y.-X. Chen研究团队经过不懈努力，在超碱介导的选择性聚合中，通过质子触发的拓扑转化使获得超高摩尔质量的环状聚合物成为可能。相关论文于2024年4月22日发表在《自然—化学》杂志上。

据了解，选择性合成超高摩尔质量(UHMM, 2 MDa)环状聚合物具有挑战性，因为需要特殊程度的时空控制来克服，可能与期望的分子内环化相竞争的不希望发生的反应。

在该研究中，该课题组人员提出了一种反直觉的环状聚合物合成方法，以聚硫酯为代表，通过超碱介导的gem-二甲基化硫丙内酯开环聚合，然后通过质子猝灭引发大分子环化进行。这种质子触发的线性到环状拓扑转换可以选择性地获得所需的环状聚硫酯，包括那些超高摩尔质量(UHMM)超过2MDa的聚硫酯。

此外，该方法不需要严格的条件，如高稀释来防止或抑制线性聚合物污染物，并提出了相反的情况，即需要无质子的条件来防止环状聚合物的形成，这被用于按需生产环状聚合物。此外，这种UHMM环聚酯不仅表现出更强的热稳定性和机械韧性，而且由于其gem-双取代，它还可以在温和的条件下定量地再循环回单体。

附：英文原文

Title: Proton-triggered topological transformation in superbase-mediated selective polymerization enables access to ultrahigh-molar-mass cyclic polymers

Author: Zhou, Li, Reilly, Liam T., Shi, Changxia, Quinn, Ethan C., Chen, Eugene Y.-X.

Issue&Volume: 2024-04-22

Abstract: The selective synthesis of ultrahigh-molar-mass (UHMM, >2millionDa) cyclic polymers is challenging as an exceptional degree of spatiotemporal control is required to overcome the possible undesired reactions that can compete with the desired intramolecular cyclization. Here we present a counterintuitive synthetic methodology for cyclic polymers, represented here by polythioesters, which proceeds via superbase-mediated ring-opening polymerization of gem-dimethylated thiopropiolactone, followed by macromolecular cyclization triggered by protic quenching. This proton-triggered linear-to-cyclic topological transformation enables selective, linear polymer-like access to desired cyclic polythioesters, including those with UHMM surpassing 2MDa. In addition, this method eliminates the need for stringent conditions such as high dilution to prevent or suppress linear polymer contaminants and presents the opposite scenario in which protic-free conditions are required to prevent cyclic polymer formation, which is capitalized to produce cyclic polymers on demand. Furthermore, such UHMM cyclic polythioester exhibits not only much enhanced thermostability and mechanical toughness, but it can also be quantitatively recycled back to monomer under mild conditions due to its gem-disubstitution.

DOI: 10.1038/s41557-024-01511-2

Source: https://www.nature.com/articles/s41557-024-01511-2