Topology Transformation toward Cyclic, Figure-Eight-Shaped, and Cross-Linked Polymers Based on the Dynamic Behavior of a Bis(hindered amino)disulfide Linker
Topology Transformation toward Cyclic, Figure-Eight-Shaped, and Cross-Linked Polymers Based on the Dynamic Behavior of a Bis(hindered amino)disulfide Linker
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DOI：
10.1021/acs.macromol.1c01437
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发表时间：
2021-10
期刊：
影响因子：
5.5
通讯作者：
Hirogi Yokochi;Masashi Ohira;M. Oka;S. Honda;Xiang Li;D. Aoki;H. Otsuka
中科院分区：
文献类型：
--
作者：
Hirogi Yokochi;Masashi Ohira;M. Oka;S. Honda;Xiang Li;D. Aoki;H. Otsuka
近几十年来，通过动态共价化学对聚合物结构进行拓扑转换引起了人们的广泛关注，因为它们改变了聚合物结构的初级结构，从而改变了聚合物的性质。然而，生成循环拓扑的拓扑转换仍然具有挑战性。本研究根据双（2,2,6,6-四甲基哌啶-1-酰基）二硫化键（BiTEMPS）的动力学行为合成了各种环状聚合物。将线性和4支聚合物转化为环状拓扑结构，即环状聚合物和8字形聚合物，其顺序如下：(1)通过巯基反应将BiTEMPS单元引入待环化聚合物的末端结构；(2)通过稀释和加热诱导BiTEMPS单元的交换反应进行熵驱动转换，得到所需的循环拓扑结构；(3)通过与表面含有悬垂巯基的聚苯乙烯颗粒进行硫醇-烯咔嗒反应，并进行简单过滤，选择性去除具有活性基团的无环杂质。BiTEMPS在加热后产生的自由基对包括氧和烯烃在内的多种化学物质具有很高的耐受性，并且在交换反应中表现出很高的反应活性，使其适用于各种骨架。通过高效的克级合成环状和数字8形聚合物，证明了该过程的简单性和底物的多功能性。此外，我们描述了所获得的环状和/或数字8型聚合物的拓扑转换为具有控制物理性质的交联聚合物，使用它们的环状或数字8拓扑和BiTEMPS单元在其结构中的动态性质。
Topology transformations of polymer architectures via dynamic covalent chemistry have attracted considerable attention in recent decades, as they change the primary structure of the polymer architecture and thus the polymer properties. However, topology transformations to produce cyclic topologies remain challenging. In this study, various cyclic polymers were synthesized based on the dynamic behavior of the bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) linkage. Linear and 4-branched polymers were transformed into cyclic topologies, namely, cyclic polymers and figure-eight-shaped polymers, using the following sequence: (1) A thiol–ene reaction was used to introduce BiTEMPS units into the terminal structures of the polymers to be cyclized; (2) an entropy-driven transformation to give the desired cyclic topology through the exchange reaction of the BiTEMPS units was induced by dilution and heating; (3) acyclic impurities with reactive groups were selectively removed via a thiol–ene click reaction with polystyrene particles that contain dangling thiol groups on their surface and subsequent simple filtration. The radicals generated by BiTEMPS upon heating are highly tolerant toward a variety of chemical species, including oxygen and olefins, and exhibit high reactivity in exchange reactions, making them applicable for various skeletons. The simplicity and substrate versatility of this procedure are demonstrated via the highly efficient gram-scale synthesis of cyclic and figure-eight-shaped polymers. Moreover, we describe the topology transformation of the obtained cyclic and/or figure-eight-shaped polymers into cross-linked polymers with controlled physical properties using their cyclic or figure-eight topology and the dynamic nature of the BiTEMPS units in their structures.