An Organometallic Super‐Gelator with Multiple‐Stimulus Responsive Properties
An Organometallic Super‐Gelator with Multiple‐Stimulus Responsive Properties
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DOI：
10.1002/adma.200703195
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发表时间：
2008-07
影响因子：
29.4
通讯作者：
Jing Liu-;P. He;Junlin Yan;Xiaohua Fang;Junxia Peng;Kaiqiang Liu;Yu Fang
中科院分区：
文献类型：
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作者：
Jing Liu-;P. He;Junlin Yan;Xiaohua Fang;Junxia Peng;Kaiqiang Liu;Yu Fang
刺激响应性凝胶作为一种新型功能材料在传感器、执行器、形状记忆、药物输送装置和显示器等方面有着广泛的应用前景。基于低分子量有机胶凝剂（LMOG）的有机凝胶可以提供的有希望的性质之一是它们作为外部刺激的结果的可逆溶胶-凝胶相转变。然而，据我们所知，来自LMOG的氧化还原响应性有机凝胶是有限的。Shinkai和同事报道了这种有机凝胶的第一个例子，它含有氧化还原活性Cu/ Cu中心。此外，他们还合成了一系列在α-位上带有两个胆固醇基的四噻吩、五噻吩和六噻吩衍生物。研究发现，通过添加氧化剂和还原剂可以实现溶胶-凝胶相变。Zhu及其同事制备了一种含有四硫富瓦烯（TTF）实体的电活性LMOG。凝胶形成可以通过化学或电化学的TTF基团的氧化/还原来调节。虽然这些凝胶系统是氧化还原响应的，但它们的性质，如机械强度、柔韧性和对外部刺激的敏感性，与实际应用所需的那些相差甚远。因此，创造即时的、可逆的、氧化还原响应的和机械柔性的有机凝胶仍然是一个挑战。作为一种显著的有机金属化合物，二茂铁（Fc）含有可氧化的金属离子Fe，并且在中性状态下是非极性化合物，因此它容易溶解在烃溶剂中。然而，这种性质可以通过简单的中心离子氧化而容易地逆转。我们对刺激响应超分子凝胶系统的兴趣使我们考虑该化合物作为一个中性阳离子氧化还原对，可以用来调节含有它的胶凝剂的胶凝能力。实际上，同样的想法已经被许多研究小组采用，用于研究胶束和囊泡中的可切换络合和分子聚集。然而，所有的COM-
Stimulus-responsive gels have recently attracted widespread attention as new functional materials for potential applications in sensors, actuators, shape memories, drug delivery devices, and displays. One of the promising properties that organogels based on low molecular mass organic gelators (LMOGs) can offer is their reversible sol–gel phase transition as a result of external stimuli. As far as we know, redoxresponsive organogels from LMOGs, however, are limited. Shinkai and coworkers reported the first example of organogels of this kind, which contains a redox-active Cu/ Cu center. Besides, they also synthesized a series of quater-, quinque-, and sexithiophene derivatives bearing two cholesteryl moieties at the a-position. It was found that a sol–gel phase transition can be implemented by addition of oxidizing and reducing reagents. Zhu and colleagues prepared an electro-active LMOG containing a tetrathiafulvalene (TTF) entity. The gel formation can be tuned by means of oxidation/ reduction of the TTF group chemically or electrochemically. Although these gel systems are redox responsive, their properties, such as mechanical strength, flexibility, and sensitivity to external stimulus, are far from those required for practical uses. Therefore, creating instant, reversible, redox-responsive, and mechanically flexible organogels still remains a challenge. As a remarkable organometallic compound, ferrocene (Fc) contains an oxidizable metal ion, Fe, and is a nonpolar compound in the neutral state, and thereby it dissolves readily in hydrocarbon solvents. This property, however, can be easily reversed by simple oxidation of the central ion. Our interest in stimulus-responsive supramolecular gel systems led us to consider the compound as a neutral–cation redox pair that may be employed to tune the gelling ability of a gelator containing it. Actually, the same idea has been adopted by a number of groups for studies of switchable complexation and molecular aggregation in micelles and vesicles. However, all com-