Azobenzene-Based Light-Responsive Hydrogel System
Azobenzene-Based Light-Responsive Hydrogel System
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DOI：
10.1021/la804316u
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发表时间：
2009-08-04
期刊：
影响因子：
3.9
通讯作者：
Stoddart, J. Fraser
中科院分区：
文献类型：
--
作者：
Zhao, Yan-Li;Stoddart, J. Fraser
制备了脱氧胆酸修饰的β-环糊精衍生物（2）和偶氮苯支化的聚（丙烯酸）共聚物（3），并通过UV/维斯光谱、诱导圆二色谱和H-1 NMR光谱表征了2与3中的反式/顺式偶氮苯单元的缔合和解离。实验结果表明，反式偶氮苯单元强烈结合在2的空腔内，而顺式偶氮苯单元根本不结合。由2和3形成的超分子包合物（1）伴随着水凝胶的形成。研究了偶氮苯单元的顺反光致异构化引起的凝胶-溶胶和溶胶-凝胶的光响应相变。在水凝胶系统中，3中的反式偶氮苯单元包含在2的疏水空腔内。在用355 nm的UV光照射时，水凝胶被有效地转化为溶胶相，因为反式偶氮苯单元被光化学转化为它们的顺式构型，于是所得的顺式偶氮苯单元从2解离。水凝胶可以通过用450 nm的可见光照射从溶胶相回收。对于许多凝胶-溶胶和溶胶-凝胶相变循环，测量新鲜水凝胶样品的溶胀比，发现其为8.7 +/-0.7。
A deoxycholic acid-modified beta-cyclodextrin derivative (2) and an azobenzene-branched poly(acrylic acid) copolymer (3) were prepared, and the association and dissociation of 2 with the trans/cis-azobenzene units in 3 were characterized by UV/vis spectroscopy, induced circular dichroism, and H-1 NMR spectroscopy. The experimental results indicate that the trans-azobenzene units are bound strongly within the cavities of 2 whereas the cis-azobenzene is not bound at all. A supramolecular inclusion complex (1), formed by 2 and 3, is accompanied by the formation of a hydrogel. The light-responsive gel-to-sol and sol-to-gel phase transitions of the hydrogel, induced by trans-cis photoisomerization of the azobenzene units, were investigated. In the hydrogel system, the trans-azobenzene units in 3 are included inside the hydrophobic cavity of 2. Upon photoirradiation with UV light of 355 nm, the hydrogel is converted efficiently to the sol phase because the trans-azobenzene units are converted photochemically to their cis configurations, whereupon the resulting cis-azobenzene units dissociate from 2. The hydrogel can be recovered from the sol phase by photoirradiation with visible light of 450 nm. The swelling ratio for fresh hydrogel samples, which was found to be 8.7 +/- 0.7, was measured for a number of gel-to-sol and sol-to-gel phase-transition cycles.