Functionalized Molecular Bottlebrushes

A three-step synthetic strategy is established for the preparation of functionalized bottlebrush copolymers. In this scheme, the highly efficient nature of thiol-epoxy coupling chemistry is employed for the attachment of thiol terminated poly(ethylene glycol) (PEG) polymers (0.18, 0.8, and 2 kDa) to the poly(glycidyl methacrylate) (PGMA) backbone (25 and 46 kDa). This coupling reaction resulted in the formation of water-soluble bottlebrush copolymers (50-426 kDa) with grafting densities ranging from 88 to 97%. The coupling process also produced reactive hydroxyl groups in the vicinity of the polymer backbone. These hydroxyl groups could be functionalized with pyrene (a fluorescent probe) or biotin (a biological ligand) molecules through an esterification reaction. Therefore, fluorescent/biorelevant bivalent bottlebrushes could be obtained in three linear synthetic steps starting from a commercially available monomer. The prepared polymers displayed structure dependent thermal and optical properties, and single bottlebrushes could be visualized with the help of atomic force microscopy (AFM).