Šantić Ana, Brinkkötter Marc, Portada Tomislav, Frkanec Leo, Cremer Cornelia, Schönhoff Monika, Moguš-Milanković Andrea
Laboratory for Functional Materials, Division of Materials Chemistry, Ruđer Bošković Institute Bijenička c. 54 10000 Zagreb Croatia
Institute of Physical Chemistry, University of Muenster Corrensstraße 28/30 48149 Münster Germany.
RSC Adv. 2020 Apr 30;10(29):17070-17078. doi: 10.1039/d0ra01249a. eCollection 2020 Apr 29.
Supramolecular ionogels composed of an ionic liquid (IL) immobilized in a network of self-assembled low-molecular weight molecules have been attracting considerable interest due to their applicability as smart electrolytes for various electrochemical applications. Despite considerable scientific effort in this field, the design of a mechanically and thermally stable yet highly conductive supramolecular ionogels still remains a challenge. In this article, we report on a series of novel ionogels of three ILs containing different cations (imidazolium/pyrrolidinium) and anions (tetrafluoroborate/bis(trifluoromethylsulfonyl)imide) prepared using (,)-bis(amino alcohol)oxamides as gelators. The gelation behaviour of the oxamide compound depends strongly on the structural features of amino alcohol substituents. Among them, (,)-bis(valinol)oxamide (capable of gelling all three ILs) and (,)-bis(phenylalaninol)oxamide (capable of gelling ILs based on bis(trifluoromethylsulfonyl)imide with a concentration as low as ≈0.2 wt%) are highly efficient. All investigated supramolecular ionogels retain the high ionic conductivity and ion diffusion coefficients of their parent IL, even for high gelator concentrations. Further, at low temperatures we observe an enhancement of the ionic conductivity in ionogels of (i) 1-butyl-3-methylimidazolium tetrafluoroborate which can be attributed to specific interactions between ionic species and gelator molecules and (ii) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide due to inhibited crystallization. In contrast to ionic transport, mechanical strength of the ionogels shows a wider variation depending on the type and concentration of the oxamide gelator. Among all the ionogels, that of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide prepared with 1 wt% (,)-bis(phenylalaninol)oxamide exhibits the best performance: optical transparency, stability over a wide temperature range, high conductivity and high mechanical strength. The results presented here reveal the versatile nature of bis(amino alcohol)oxamides as gelators and their high potential for preparing functionalized IL-based materials.
由固定在自组装低分子量分子网络中的离子液体（IL）组成的超分子离子凝胶，因其作为各种电化学应用的智能电解质的适用性而备受关注。尽管在该领域进行了大量的科学研究，但设计一种机械和热稳定且高导电的超分子离子凝胶仍然是一项挑战。在本文中，我们报道了一系列新型离子凝胶，它们由三种含有不同阳离子（咪唑鎓/吡咯烷鎓）和阴离子（四氟硼酸根/双（三氟甲基磺酰）亚胺）的离子液体使用（，）-双（氨基醇）草酰胺作为凝胶剂制备而成。草酰胺化合物的凝胶化行为强烈依赖于氨基醇取代基的结构特征。其中，（，）-双（缬氨醇）草酰胺（能够使所有三种离子液体凝胶化）和（，）-双（苯丙氨醇）草酰胺（能够使基于双（三氟甲基磺酰）亚胺的离子液体凝胶化，浓度低至≈0.2 wt%）效率很高。所有研究的超分子离子凝胶即使在高凝胶剂浓度下也保留了其母体离子液体的高离子电导率和离子扩散系数。此外，在低温下，我们观察到（i）1-丁基-3-甲基咪唑鎓四氟硼酸盐的离子凝胶中的离子电导率增强，这可归因于离子物种与凝胶剂分子之间的特定相互作用，以及（ii）1-丁基-3-甲基咪唑鎓双（三氟甲基磺酰）亚胺由于结晶受到抑制而导致的离子电导率增强。与离子传输相反，离子凝胶的机械强度根据草酰胺凝胶剂的类型和浓度表现出更广泛的变化。在所有离子凝胶中，用1 wt%的（，）-双（苯丙氨醇）草酰胺制备的1-丁基-3-甲基咪唑鎓双（三氟甲基磺酰）亚胺的离子凝胶表现出最佳性能：光学透明度、在宽温度范围内的稳定性、高电导率和高机械强度。此处呈现的结果揭示了双（氨基醇）草酰胺作为凝胶剂的多功能性质及其制备功能化离子液体基材料的巨大潜力。
