Departamento de Química Orgánica, Facultad de Ciencias Químicas, Ciudad Universitaria, s/n. 28040 Madrid, Spain.
Chemistry. 2010 Mar 8;16(10):3138-46. doi: 10.1002/chem.200902894.
Triangular-shaped oligo(phenylene ethynylene) amphiphiles 1a and 1b decorated in their periphery with two- and four-branched hydrophilic triethyleneglycol dendron wedges, have been synthesized and their self-assembling properties in solution and onto surfaces investigated. The steric demand produced by the dendritic substituents induces a face-to-face rotated pi stacking of the aromatic moieties. Studies on the concentration and temperature dependence confirm this mechanism and provide binding constants of 1.2 x 10(5) and 1.7 x 10(5) M(-1) in acetonitrile for 1a and 1b, respectively. Dynamic and static light scattering measurements complement the study of the self-assembly in solution and demonstrate the formation of rod-like supramolecular structures in aqueous solution. The nanofibers formed in solution can be efficiently transferred onto surfaces. Thus, TEM images reveal the presence of strands of various thickness, with the most common being several micrometers long and with diameters of around 70 nm. Some of these nanofibers present folded edges that are indicative of their ribbon-like nature. Interestingly, compound 1b can also form thick filaments with a rope-like appearance, which points to a chiral arrangement of the fibers. AFM images under highly diluted conditions also reveal long fibers with height profiles that fit well with the molecular dimensions calculated for both amphiphiles. Finally, we have demonstrated the intercalation of the hydrophobic dye Disperse Orange 3 within the filaments and its subsequent release upon increasing the temperature.
具有三角形形状的寡聚（苯乙炔）两亲分子 1a 和 1b 在其外围用两个和四个分支的亲水性三乙二醇树枝状楔形物进行了修饰，已经被合成，并研究了它们在溶液中和表面上的自组装性质。树枝状取代基产生的空间位阻导致芳香部分的面对面旋转 π 堆积。对浓度和温度依赖性的研究证实了这一机制，并分别为 1a 和 1b 在乙腈中提供了 1.2 x 10(5)和 1.7 x 10(5) M(-1)的结合常数。动态和静态光散射测量补充了溶液中自组装的研究，并证明了在水溶液中形成棒状超分子结构。在溶液中形成的纳米纤维可以有效地转移到表面上。因此，TEM 图像显示存在各种厚度的链，最常见的是几微米长，直径约为 70nm。其中一些纳米纤维具有折叠边缘，表明它们具有带状性质。有趣的是，化合物 1b 也可以形成具有绳索状外观的厚纤维，这表明纤维的手性排列。在高度稀释的条件下，AFM 图像也显示出具有与两种两亲分子计算出的分子尺寸相匹配的高度轮廓的长纤维。最后，我们已经证明了疏水性染料 Disperse Orange 3 可以插入纤维中，并在温度升高时释放。
