Solvent-mediated gel formation, hierarchical structures, and rheological properties of organogels.
Solvent-mediated gel formation, hierarchical structures, and rheological properties of organogels.
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DOI：
10.1039/c4sm02423k
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发表时间：
2015-01
期刊：
影响因子：
3.4
通讯作者：
Mingxing Su;Haikuan Yang;Li-jun Ren;Ping Zheng;Wei Wang
中科院分区：
文献类型：
--
作者：
Mingxing Su;Haikuan Yang;Li-jun Ren;Ping Zheng;Wei Wang
我们报告的溶剂介导的凝胶的形成以及它们的层次结构和流变性能。所使用的胶凝剂是具有胆固醇-聚氧乙烯酸酯-胆固醇的分子结构的杂化物，其中胆固醇在甲苯和N，N-二甲基甲酰胺（DMF）中溶解良好，而聚氧乙烯酸酯簇仅溶解于DMF中。当甲苯的体积分数ftol大于85.7v/v%时，这些溶解度差异使凝胶因子能够通过混合溶剂甲苯和DMF形成热可逆的超分子有机凝胶。我们发现凝胶化时间、tgel和ftol之间呈V形相关：当ftol从85.7 v/v%增加到90.0 v/v%时，tgel从1300 min减少到2 min。然后，当ftol从90.0 v/v%进一步增加到100.0 v/v%时，其从2 min增加到5800 min。我们观察到的带状自组装结构的凝胶，以及从刚性和直的带状扭曲的从ftol=85.7 v/v%到ftol=100.0 v/v%的结构演变。这些带状物构成两个三维（3D）凝胶网络：一个是通过刚性和直带状物的物理连接构建的，另一个是通过带状物分裂和缠绕构建的。后者具有更好的3D凝胶网络，提供更好的流变性能。从根本上说，这种溶剂介导的方法调节了该胶凝剂在混合溶剂中的溶解度和不溶解度之间的平衡。这也为有机凝胶的制备提供了一种新的方法。
We report the formation of solvent-mediated gels as well as their hierarchical structures and rheological properties. The gelator used is a hybrid with a molecular structure of cholesterol-polyoxometalate-cholesterol, in which the cholesterol dissolves well in toluene and N,N-dimethylformamide (DMF), whereas the polyoxometalate cluster dissolves only in DMF. These solubility differences enable the gelator to form thermally reversible supramolecular organogels by mixing solvents of toluene and DMF when the volume fraction, ftol, of toluene is larger than 85.7 v/v%. We found a V-shaped correlation between the gelation times, tgel and ftol: tgel decreases from 1300 min to 2 min when ftol increases from 85.7 v/v% to 90.0 v/v%. It then increases from 2 min to 5800 min when ftol further increases from 90.0 v/v% to 100.0 v/v%. We observed ribbon-like self-assembled structures in the gels as well as a structural evolution from rigid and straight ribbons to twistable ones from ftol=85.7 v/v% to ftol=100.0 v/v%. These ribbons constitute two three-dimensional (3D) gel networks: one is constructed via physical connection of the rigid and straight ribbon, and the other is built up from ribbons splitting and intertwining. The latter has a better 3D gel network that offers improved rheological properties. Fundamentally, this solvent-mediated approach regulates the balance between solubility and insolubility of this gelator in the mixing solvents. It also provides a new method for the preparation of organogels.