Scalable Synthesis of Multivalent Macromonomers for ROMP

The polymerization of functional monomers provides direct access to functional polymers without need for postpolymerization modification; however, monomer synthesis can become a bottleneck of this approach. New methods that enable rapid installation of functionality into monomers for living polymerization are valuable. Here, we report the three-step convergent synthesis (two-step longest linear sequence) of a divalent exo-norbornene imide capable of efficient coupling with various nucleophiles and azides to produce diversely functionalized branched macromonomers optimized for ring-opening metathesis polymerization (ROMP). In addition, we describe an efficient iterative procedure for the synthesis of tri- and tetra-valent branched macromonomers. We demonstrate the use of these branched macromonomers for the synthesis of Janus bottlebrush block copolymers as well as for the generation of bottlebrush polymers with up to three conjugated small molecules per repeat unit. This work significantly expands the scalability and diversity of nanostructured macromolecules accessible via ROMP.