College of Science, and Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology , Yuhua Road 70, Shijiazhuang 050080, P. R. China.
ACS Appl Mater Interfaces. 2017 Apr 19;9(15):13666-13675. doi: 10.1021/acsami.6b15249. Epub 2017 Apr 6.
In this study, we show that a novel kind of cholesterol-based gelator NPS containing pyridyl and naphthalimide units can visually discriminate cyclohexane/cyclopentane from hexane/pentane on the basis of distinct optical differences in the gel platform, which is not observed in solution. The effect of congeneric solvents on the gel properties, such as morphology, rheology, and stimuli-responsive properties, is also studied. Intriguingly, NPS can form self-supporting, self-healing, fluorescent, and highly visible transmittance gels in cyclohexane that can selectively and visually respond to picric acid. It is deduced that NPS adopted H-type aggregation mode in cyclohexane, and the gel exhibits a strong green emission, whereas, in hexane, J-type aggregates of NPS molecules are observed with yellow emission. Correlations between the gelation properties and Hansen solubility parameters indicate that the dispersion interactions are the main factor for the selective gelation of NPS toward short-chain alkanes. A comparison of Hansen solvent parameters indicated that a similar energetic weight of the hydrogen-bonding units is the major contribution for the strong and specific interaction between NPS and cyclohexane. Furthermore, we demonstrated that the NPS xerogel can selectively solidify cyclohexane in the single-phase liquid of solvent mixtures, exhibiting fast gelation, high separation efficiency (>92%), and easy recycling of gelator and liquids. To the best of our knowledge, herein, we report the first paradigm that molecular gel formation is developed to visually discriminate and separate organic analogues of solvents with similar polarity.
在这项研究中，我们展示了一种新型的基于胆固醇的凝胶剂 NPS，它含有吡啶和萘酰亚胺单元，可以根据凝胶平台上明显的光学差异，在视觉上区分环己烷/环戊烷与己烷/戊烷，而在溶液中则观察不到这种差异。还研究了同类溶剂对凝胶性质的影响，如形态、流变学和刺激响应性质。有趣的是，NPS 可以在环己烷中形成自支撑、自修复、荧光和高可见透光率的凝胶，可以选择性地和可视化地响应苦味酸。据推断，NPS 在环己烷中采用 H 型聚集模式，凝胶表现出强烈的绿色发射，而在己烷中，观察到 NPS 分子的 J 型聚集，发射黄色。凝胶性质与 Hansen 溶解度参数之间的相关性表明，分散相互作用是 NPS 对短链烷烃选择性凝胶化的主要因素。对 Hansen 溶剂参数的比较表明，氢键单元的相似能量权重是 NPS 与环己烷之间强而特异相互作用的主要贡献。此外，我们证明了 NPS 干凝胶可以在溶剂混合物的单相液体中选择性地固化环己烷，表现出快速凝胶化、高分离效率（>92%）和凝胶剂和液体的易于回收。据我们所知，本文首次报道了一种范例，即通过分子凝胶形成来可视化区分和分离具有相似极性的溶剂的有机类似物。
