Multifunctional Vesicles from a Self-assembled Cluster-Containing Diblock Copolymer

We describe a new diblock copolymer composed of two segments with complementary functionalities. One block contains pendent photo-cross-linkable cinnamoyl groups, and the other contains molecular clusters, Co6Se8, capable of multielectron redox processes. This multifunctional macromolecule is synthesized by sequential ring-opening metathesis polymerization of monomers constructed using norbornene moieties. Remarkably, the tethered molecular cluster gives access to three different charge states in N,N-dimethylformamide: neutral, +1, and +2. In tetrahydrofuran, by contrast, the charged copolymer self-assembles into vesicles that inhibit the redox reactions. The wall of these vesicles can be cross-linked by exploiting the photoinduced 2 + 2 cycloaddition of the cinnamoyls to form cyclobutane dimers. Moreover, these vesicles can be loaded with molecular cargo and used as cross-linkable containers; we demonstrate this feature by encapsulating the molecular dye methylene blue into the capsules. Our work is the first report of a well-defined block copolymer containing a metal chalcogenide molecular cluster; more generally, it opens the door to new applications of metal-containing polymers.我们报道了一种由两段具有互补官能团的新型双嵌段共聚物。其中一条嵌段侧连有可光交联的肉桂酰基，另一条嵌段则搭载有能够发生多电子氧化还原过程的分子团簇Co6Se8。该多功能大分子通过以降冰片烯为结构单元构建的单体，经顺序开环易位聚合（sequential ring-opening metathesis polymerization）合成。值得注意的是，在N,N-二甲基甲酰胺（N,N-dimethylformamide）溶剂中，锚定的分子团簇可呈现三种不同的电荷态：中性、+1价与+2价。与之相对，在四氢呋喃（tetrahydrofuran）溶剂中，带电的共聚物会自组装形成囊泡，该囊泡能够抑制氧化还原反应。借助肉桂酰基的光诱导2+2环加成（photoinduced 2 + 2 cycloaddition）反应生成环丁烷二聚体，可对这些囊泡的壁进行交联固定。此外，这类囊泡可负载分子载荷，并作为可交联容器使用；我们通过将分子染料亚甲基蓝包埋入胶囊状结构中，验证了这一应用特性。本研究首次报道了一种含有金属硫族化合物分子团簇（metal chalcogenide molecular cluster）的结构明确的嵌段共聚物；更广泛而言，该工作为含金属聚合物（metal-containing polymers）的全新应用场景打开了大门。