Developing robust hydrogel materials with stimulus responsiveness to apolar organic vapors or gases is significantly challenging due to the deficient interaction between solvents and gelators, the intrinsic colloidal stability of gels toward low content solvent molecules in the gas phase and their immiscibility. We herein report unprecedented aromatic vapor responsive hydrogels taking advantage of the convenient crystal transformation phenomenon of commercially available β-cyclodextrin (β-CD). One-dimensional crystallization-induced self-assembly in a dimethyl formamide (DMF)/water mixture with specific proportions allows for the formation of stable gels. The hydrogel could selectively transform into crystalline precipitates upon exposure to aromatic solvent vapors. The phase transition is initiated through a cage-type to a channel-type single crystal transformation with a gradual solvent etching process, in which the CH–π interaction between DMF and the benzene ring confined within β-CD dimers is regarded as the primary driving force. We demonstrated that this unique gel system could act as an efficient sensor and adsorbent for hazardous aromatic vapors indoors. In addition, binary organic–inorganic hydrogel composites coassembled by clay with β-CD showed haze evolution toward aromatic vapor and heating–cooling treatment, accompanied by mechanical strength enhancement dependent on the building unit proportion. The present research opens an avenue to apply hydrogels in selectively sensing/adsorbing organic vapors, and would pave an alternative route for further development of responsive soft materials.

中文翻译：

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超分子凝胶中的芳香蒸气反应性分子堆积重排

由于溶剂和胶凝剂之间的相互作用不足，凝胶对气相中低含量溶剂分子的固有胶体稳定性及其不混溶性，因此开发出对非极性有机蒸气或气体具有刺激响应能力的坚固水凝胶材料具有很大的挑战性。我们在本文中报道了前所未有的芳香族蒸气响应性水凝胶，它利用了可商购的β-环糊精（β-CD）的便捷晶体转变现象。在特定比例的二甲基甲酰胺（DMF）/水混合物中，一维结晶诱导的自组装可形成稳定的凝胶。当暴露于芳族溶剂蒸汽中时，水凝胶可以选择性地转化为结晶沉淀。通过逐步溶剂蚀刻工艺，通过笼型到沟道型单晶转变开始相变，其中，DMF和封闭在β-CD二聚体中的苯环之间的CH-π相互作用被认为是主要驱动力力。我们证明了这种独特的凝胶系统可以用作室内有害芳香蒸气的有效传感器和吸附剂。此外，由粘土与β-CD共同组装而成的二元有机-无机水凝胶复合材料显示出雾状向芳香族蒸气的扩散和加热-冷却处理，同时机械强度的提高取决于建筑单元的比例。本研究开辟了一条途径，将水凝胶用于选择性地感测/吸附有机蒸气，并为进一步开发响应性软材料铺平了另一条途径。