Simple design but marvelous performances: molecular gels of superior strength and self-healing properties
作者:Zhiyan Xu、Junxia Peng、Ni Yan、Hang Yu、Shasha Zhang、Kaiqiang Liu、Yu Fang
DOI:10.1039/c2sm27208c
日期:——
Four nitrobenzoxadiazole (NBD)-containing cholesteryl (Chol) derivatives were prepared, and their gelation behaviors were tested. It was demonstrated that the compounds show a remarkable gelling ability. In particular, a subtle change in the length of the spacers connecting the two structural units of the compounds, which are NBD and Chol, respectively, produced a dramatic change in the gelation ability and the gel properties of the compounds. As for gelation, compound 1 is much more powerful than others, especially in the gelation of methanol-containing organic mixtures. It is to be noted that the gel of 1/pyridine–methanol exhibits superior mechanical strength with a yield stress higher than 6300 Pa at a gelator concentration of 2.5% (w/v), and the value exceeds 23 000 Pa when the gelator concentration reaches 5.0% (w/v), a result never reported before in the field of molecular gels based on low-molecular mass gelators (LMMGs). More importantly, the gel shows a rapid self-healing property as evidenced by the fact that the gel heals up immediately upon cutting, provided the segments from the cutting are squeezed together. No doubt, our findings establish a benchmark for LMMG-based molecular gels in their rheological performances. FTIR, 1H NMR and XRD studies revealed that intermolecular hydrogen bonding and π–π stacking are two of the main driving forces to promote the gelation of the system and the self-assembling of the molecules of the gelator.
研究人员制备了四种含硝基苯并噁二唑(NBD)的胆固醇(Chol)衍生物,并测试了它们的凝胶行为。结果表明,这些化合物具有显著的胶凝能力。特别是,连接化合物两个结构单元(分别为 NBD 和 Chol)的间隔物的长度发生微妙变化,化合物的凝胶能力和凝胶特性就会发生巨大变化。在凝胶化方面,化合物 1 的凝胶化能力远远强于其他化合物,尤其是在含甲醇有机混合物的凝胶化方面。值得注意的是,1/吡啶-甲醇的凝胶显示出卓越的机械强度,在凝胶剂浓度为 2.5%(w/v)时,屈服应力高于 6300 Pa,当凝胶剂浓度达到 5.0%(w/v)时,屈服应力超过 23 000 Pa,这在基于低分子质量凝胶剂(LMMGs)的分子凝胶领域是从未报道过的。更重要的是,凝胶具有快速自愈合的特性,只要将切割后的凝胶段挤压在一起,凝胶就能在切割后立即愈合。毫无疑问,我们的研究结果为基于 LMMG 的分子凝胶的流变性能确立了一个基准。傅立叶变换红外光谱、1H NMR 和 XRD 研究表明,分子间氢键和 π-π 堆积是促进体系凝胶化和凝胶剂分子自组装的两个主要驱动力。