Synthetic Strategy for Mechanically Interlocked Cyclic Polymers via the Ring-Expansion Polymerization of Macrocycles with a Bis(hindered amino)disulfide Linker
Synthetic Strategy for Mechanically Interlocked Cyclic Polymers via the Ring-Expansion Polymerization of Macrocycles with a Bis(hindered amino)disulfide Linker
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DOI：
10.1021/acs.macromol.1c01067
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发表时间：
2021-09
期刊：
影响因子：
5.5
通讯作者：
Rikito Takashima;D. Aoki;H. Otsuka
中科院分区：
文献类型：
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作者：
Rikito Takashima;D. Aoki;H. Otsuka
含有轮烷和顺丁烯结构的机械互锁聚合物由于其互锁结构的有限迁移率和与共价键相当的稳健性而引起了人们的广泛关注。在这些聚合物中，机械互锁的环状聚合物(MICP)作为一种具有较大可移动面积的新型聚合物显示出巨大的潜力。然而，通往MICP的合成路线并未得到很好的开发，创建MICP仍然具有挑战性。本研究将环状二硫键单体的扩环聚合与超分子相互作用相结合，为MICP的合成提供了一种有效的方法。合成了由双(受阻氨基)二硫化物(BiTEMPS)连接体和超分子部分组成的大环单体(MMS)，它们能形成1/1电荷转移络合物。这些MMS被用在体态的热诱导反应中，通过BiTEMPS的分子间交换反应导致它们快速聚合。通过测定储能模数G‘的增加来监测聚合过程中力学性能的变化。重要的是，含有NDI和DAN的MMS的本体共聚增加了所得共聚物的流体力学体积，这是由于聚合物链的空间纠缠所致。所得聚合物的物理性质的变化与由相同单体制成的线性拓扑的聚合物形成鲜明对比，从而支持MICP的形成。这些结果为MICP的成功设计提供了指导，即MMS的动态性质和超分子相互作用的结合。鉴于本方法具有很强的通用性，可望适用于各种分子骨架和超分子体系。
Mechanically interlocked polymers that contain rotaxane and catenane structures have attracted much attention on account of their unique properties arising from the restricted mobility of their interlocked structure and their robustness which are comparable to those of covalent bonds. Among these polymers, mechanically interlocked cyclic polymers (MICPs) exhibit great potential as a novel type of polymer with a large movable area of the interlocked structure. However, synthetic routes to MICPs are not well developed, and it is still challenging to create MICPs. The present study has resulted in an effective method for the synthesis of MICPs from the combination of the ring-expansion polymerization (REP) of cyclic disulfide monomers with supramolecular interactions. Macrocyclic monomers (MMs) that consist of a bis(hindered amino)disulfide (BiTEMPS) linker and a supramolecular moiety, such as naphthalenediimide (NDI) and dialkoxynaphthalene (DAN), capable of forming a strong 1/1 charge-transfer complex, were synthesized as the monomers for the subsequent REP. These MMs were used in a heat-induced REP in the bulk state, which led to their swift polymerization via an intermolecular exchange reaction of BiTEMPS. The change in mechanical properties during the polymerization was monitored by rheological measurements of the increase of the storage modulus,G′. Importantly, the bulk copolymerization of the MMs containing NDI and DAN increased the hydrodynamic volume of the resulting copolymers, which is due to the spatial entanglement of the polymer chains. The change in the physical properties of the resulting polymers stands in sharp contrast to that observed in polymers with a linear topology made from the same monomers, thus supporting the formation of MICPs. The results provide guidelines for the successful design of MICPs, that is, a combination of the dynamic nature of the MMs and supramolecular interactions. Given that the present method is highly versatile, it can be expected to be applicable to various molecular skeletons and supramolecular systems.