Houmadi S, Coquière D, Legrand L, Fauré M C, Goldmann M, Reinaud O, Rémita S
Institut des Nano-Sciences de Paris (INSP, CNRS, Université Paris VI, UMR 7588), Université Pierre et Marie Curie, Campus Boucicaut, 140 rue de Lourmel, 75015 Paris, France.
Langmuir. 2007 Apr 24;23(9):4849-55. doi: 10.1021/la700271a. Epub 2007 Mar 31.
Self-assemblies of a calix[6]arene (1) functionalized at the small rim by three imidazolyl arms and at the large rim by three hydrophilic sulfonato groups have been studied in water. Transmission electron microscopy, atomic force microscopy, and in situ dynamic light scattering showed that 1 forms multilamellar vesicles at a concentration equal to 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 smaller size are obtained. The impact of the pH and the presence of Ag+ ions have also been investigated. Whereas increasing the 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 pKa of the tris(imidazole) core of 1. Most interestingly, in the presence of silver ions, micelles (2.5 nm large) were obtained instead of vesicles. These observations are attributable to the imidazole core in 1 that is not only sensitive to the presence of protons but also can bind a silver cation. The resulting geometrical change in the monomeric units triggers the collapse of the vesicles into micelles. This shows that the implementation of an acid-base functionality such as an imidazole group in the hydrophobic core of the amphiphilic calix[6]arene makes the aggregation architecture responsive to the pH and to metal ions.
对一种杯[6]芳烃（1）的自组装进行了研究，该杯[6]芳烃在小环上通过三个咪唑基臂官能化，在大环上通过三个亲水性磺酸根基团官能化。透射电子显微镜、原子力显微镜和原位动态光散射表明，1在浓度等于或高于10^(-4) M时形成多层囊泡。在pH 7.8和10^(-4) M时，多层囊泡呈现出相对较大的多分散性（直径为50 - 250 nm）。然而，超声处理后可获得多分散性低得多且尺寸更小的单层囊泡。还研究了pH值和Ag+离子存在的影响。虽然提高pH值会导致形成巨大囊泡（450 nm），但在仅略高于1的三（咪唑）核心的pKa的pH值（6.5）下可获得50 nm的单分散囊泡。最有趣的是，在银离子存在下，得到的是胶束（直径2.5 nm）而不是囊泡。这些观察结果归因于1中的咪唑核心，它不仅对质子的存在敏感，而且能结合银阳离子。单体单元中由此产生的几何变化引发囊泡塌缩成胶束。这表明在两亲性杯[6]芳烃的疏水核心中引入酸碱官能团（如咪唑基团）可使聚集结构对pH值和金属离子产生响应。
