Syntheses of triblock bottlebrush polymers through sequential ROMPs: Expanding the functionalities of molecular brushes

The living nature of ROMP via sequentially grafting through a series of functional NB-MMs towards functional triblock brushes was explored, which composed a hydrophilic and stealth segment, a hydrophobic segment that allows for orthogonal self-assembly, and a DNA delivery-addressable functional segment. The corresponding norbornene-terminated macromonomers (NB-MMs) with different NB anchor groups were synthesized by amidation-based couplings, ROP, and reversible addition-fragmentation chain transfer (RAFT) (co)polymerization, respectively. Aqueous assemblies of the resulting amphiphilic triblock bottlebrush copolymers with different hydrophilic/hydrophobic ratios, before and after deprotection of functional segments, were also studied. The aqueous self-assembly behavior was investigated before and after functional group transformation, which revealed different morphologies with interesting architectural features. Further investigations, including structural elucidations and nucleic acid delivery evaluations of these nanostructures, are currently underway.