Li Wei-Jian, Wang Wei, Wang Xu-Qing, Li Mu, Ke Yubin, Yao Rui, Wen Jin, Yin Guang-Qiang, Jiang Bo, Li Xiaopeng, Yin Panchao, Yang Hai-Bo
Shanghai Key Laboratory of Green Chemistry and Chemical Processes & Chang-Kung Chuang Institute, School of Chemistry and Molecular Engineering, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, People's Republic of China.
South China Advanced Institute for Soft Matter Science and Technology & State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, People's Republic of China.
J Am Chem Soc. 2020 May 6;142(18):8473-8482. doi: 10.1021/jacs.0c02475. Epub 2020 Apr 22.
The precise construction of the high-order mechanically interlocked molecules (MIMs) with well-defined topological arrangements of multiple mechanically interlocked units has been a great challenge. Herein, we present the first successful preparation of a new family of daisy chain dendrimers, in which the individual [c2]daisy chain rotaxane units serve as the branches of dendrimer skeleton. In particular, the third-generation daisy chain dendrimer with 21 [c2]daisy chain rotaxane moieties was realized, which might be among the most complicated discrete high-order MIMs comprised of multiple [c2]daisy chain rotaxane units. Interestingly, such unique topological arrangements of multiple stimuli-responsive [c2]daisy chain rotaxanes endowed the resultant daisy chain dendrimers controllable and reversible nanoscale dimension modulation through the collective and amplified extension/contraction of each [c2]daisy chain rotaxane branch upon the addition of acetate anions or DMSO molecules as external stimulus. Furthermore, on the basis of such an intriguing size switching feature of daisy chain dendrimers, dynamic composite polymer films were constructed through the incorporation of daisy chain dendrimers into polymer films, which could undergo fast, reversible, and controllable shape transformations when DMSO molecules were employed as stimulus. The successful merging of [c2]daisy chain rotaxanes and dendrimers described herein provides not only a brand-new type of high-order mechanically interlocked systems with well-defined topological arrangements of [c2]daisy chain rotaxanes, but also a successful and practical approach toward the construction of supramolecular dynamic materials.
精确构建具有多个机械互锁单元的明确拓扑排列的高阶机械互锁分子（MIMs）一直是一项巨大挑战。在此，我们首次成功制备了一类新的雏菊链树枝状大分子，其中单个[c2]雏菊链轮烷单元作为树枝状大分子骨架的分支。特别地，实现了具有21个[c2]雏菊链轮烷部分的第三代雏菊链树枝状大分子，它可能是由多个[c2]雏菊链轮烷单元组成的最复杂的离散高阶MIMs之一。有趣的是，多个刺激响应性[c2]雏菊链轮烷的这种独特拓扑排列，通过在添加醋酸根阴离子或DMSO分子作为外部刺激时，每个[c2]雏菊链轮烷分支的集体和放大的伸展/收缩，赋予了所得雏菊链树枝状大分子可控且可逆的纳米级尺寸调制。此外，基于雏菊链树枝状大分子这种引人入胜的尺寸切换特性，通过将雏菊链树枝状大分子掺入聚合物薄膜中构建了动态复合聚合物薄膜，当使用DMSO分子作为刺激时，该薄膜可以进行快速、可逆且可控的形状转变。本文所述的[c2]雏菊链轮烷与树枝状大分子的成功融合，不仅提供了一种具有明确[c2]雏菊链轮烷拓扑排列的全新类型的高阶机械互锁系统，还为构建超分子动态材料提供了一种成功且实用的方法。
