International Joint Laboratory of Biomimetic and Smart Polymers, School of Materials Science and Engineering, Shanghai University, Materials Building Room 801, Nanchen Street 380, Shanghai, 200444, P. R. China.
Chemistry. 2021 Jul 16;27(40):10470-10476. doi: 10.1002/chem.202101283. Epub 2021 Jun 7.
Water-soluble and thermoresponsive macrocycles with stable inclusion toward guests are highly valuable to construct stimuli-responsive supramolecular materials for versatile applications. Here, we develop such macrocycles - ureido-substituted cyclodextrins (CDs) which exhibit unprecedented upper critical solution temperature (UCST) behavior in aqueous media. These novel CD derivatives showed good solubility in water at elevated temperature, but collapsed from water to form large coacervates upon cooling to low temperature. Their cloud points are greatly dependent on concentration and can be mediated through oxidation and chelation with silver ions. Significantly, the amphiphilicity of these CD derivatives is supportive to host-guest binding, which affords them inclusion abilities to guest dyes. The inclusion complexation remained nearly intact during thermally induced phase transitions, which is in contrast to the switchable inclusion behavior of lower critical solution temperature (LCST)-type CDs. Moreover, ureido-substituted CDs were exploited to co-encapsulate a pair of guest dyes whose fluorescence resonance energy transfer process can be switched by the UCST phase transition. We therefore believe these novel thermoresponsive CDs may form a new strategy for developing smart macrocycles and allow for exploring smart supramolecular materials.
具有稳定客体包合性能的水溶性和温敏性大环主体对于构建用于各种应用的刺激响应超分子材料具有非常重要的价值。在这里，我们开发了这样的大环 - 脲基取代的环糊精（CD），它们在水介质中表现出前所未有的上临界溶解温度（UCST）行为。这些新型 CD 衍生物在高温下在水中具有良好的溶解性，但在冷却至低温时会从水中塌陷形成大的凝聚相。它们的浊点极大地依赖于浓度，并可以通过与银离子的氧化和螯合来调节。重要的是，这些 CD 衍生物的两亲性支持主体 - 客体结合，这为它们提供了对客体染料的包合能力。包含络合在热诱导的相转变过程中几乎保持完整，这与较低临界溶解温度（LCST）型 CD 的可切换包合行为形成对比。此外，脲基取代的 CD 被用于共包封一对客体染料，其荧光共振能量转移过程可以通过 UCST 相转变来切换。因此，我们相信这些新型温敏性 CD 可能为开发智能大环主体提供一种新策略，并允许探索智能超分子材料。
