College of Materials Science and Engineering, Zhejiang University of Technology , Hangzhou 310014, China.
Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
Langmuir. 2017 Nov 21;33(46):13332-13342. doi: 10.1021/acs.langmuir.7b02893. Epub 2017 Nov 7.
Aromatic groups are introduced into the end peripherals of polyhedral oligomeric silsesquioxane (POSS) core-based organic/inorganic hybrid supramolecules to get a novel dendrimer gelator POSS-Z-Asp(OBzl) (POSS-ASP), which have eight aspartate derivative arms to make full use of strong π-π stacking forces to get strong supramolecular gels in addition to multiple hydrogen bindings and van der Waals interactions. POSS-ASP can self-assemble into three-dimensional nanoscale gel networks to provide hybrid physical gels especially with strong mechanical properties and fast-recovery behaviors. Two totally different morphologies of the connected spherical particle structures and banded ultralong fibers are observed owing to the polarity of solvents confirmed by the scanning electron microscopy, polarized optical microscopy, and transmission electron microscopy techniques, expecting the existing various self-assembly models and illustrating the peripherals of the dendrimer and the polarity of solvents having huge influences in the supramolecular self-assembly mechanism. What is more, the thermal stability, rheological properties, and network architecture information have also been investigated via tube-inversion, rotational rheometer, and powder X-ray diffraction methods, the results of which confirm the two different gel formation mechanisms that make POSS-ASP to exhibit two totally different thermal and mechanical properties. Such a study reports a new gelation system in organic or organic/aqueous mixed solvents, which can be helpful for investigating the relationship of dendritic supramolecular gelation and different polarity solvents during the supramolecular self-assembly process of gelators.
芳香族基团被引入多面体低聚倍半硅氧烷（POSS）核基有机/无机杂化超分子的末端外围，得到一种新型的树枝状凝胶剂 POSS-Z-Asp（OBzl）（POSS-ASP），它具有八个天冬氨酸衍生物臂，除了多个氢键和范德华相互作用外，还充分利用了强π-π堆积力来获得强超分子凝胶。POSS-ASP 可以自组装成三维纳米级凝胶网络，提供混合物理凝胶，特别是具有强机械性能和快速恢复行为。通过扫描电子显微镜、偏光显微镜和透射电子显微镜技术证实了溶剂的极性，观察到了连接的球形粒子结构和带状超长纤维两种完全不同的形态，这归因于溶剂的极性，预期现有的各种自组装模型，并说明了树枝状大分子的外围和溶剂的极性对超分子自组装机制有巨大影响。此外，还通过管反转、旋转流变仪和粉末 X 射线衍射方法研究了热稳定性、流变性能和网络结构信息，结果证实了两种不同的凝胶形成机制，使 POSS-ASP 表现出两种完全不同的热学和力学性能。这项研究报告了一种在有机或有机/水混合溶剂中的新凝胶体系，这有助于研究在凝胶剂的超分子自组装过程中，树状超分子凝胶化与不同极性溶剂之间的关系。
