Architecture-Controlled "SMART" Calix[6]Arene Self-Assemblies in Aqueous Solution

详细信息    查看全文

• 作者：S. Houmadi ; D. Coquiè ; re ; L. Legrand ; M. C. Faur&eacute ; M. Goldmann ; O. Reinaud ; S. R&eacute ; mita
• 刊名：Langmuir
• 出版年：2007
• 出版时间：April 24, 2007
• 年：2007
• 卷：23
• 期：9
• 页码：4849 - 4855
• 全文大小：749K
• 年卷期：v.23,no.9(April 24, 2007)
• ISSN：1520-5827

文摘

Self-assemblies of a calix[6]arene (1) functionalized at the small rim by three imidazolyl arms and at the large rimby three hydrophilic sulfonato groups have been studied in water. Transmission electron microscopy, atomic forcemicroscopy, and in situ dynamic light scattering showed that 1 forms multilamellar vesicles at a concentration equalto or higher than 10^-4 M. At pH 7.8 and 10^-4 M, the multilamellar vesicles present a relatively large polydispersity(50-250 nm in diameter). However, after sonication unilamellar vesicles of much lower polydispersity and smallersize are obtained. The impact of the pH and the presence of Ag⁺ ions have also been investigated. Whereas increasingthe pH led to the formation of giant vesicles (450 nm), monodisperse vesicules of 50 nm were obtained at a pH (6.5)that is only slightly higher than the pK_a of the tris(imidazole) core of 1. Most interestingly, in the presence of silverions, micelles (2.5 nm large) were obtained instead of vesicles. These observations are attributable to the imidazolecore in 1 that is not only sensitive to the presence of protons but also can bind a silver cation. The resulting geometricalchange in the monomeric units triggers the collapse of the vesicles into micelles. This shows that the implementationof an acid-base functionality such as an imidazole group in the hydrophobic core of the amphiphilic calix[6]arenemakes the aggregation architecture responsive to the pH and to metal ions.