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.