High-density and hetero-functional group engineering of segmented hyperbranched polymers via click chemistry

A new kind of segmented hyperbranched polymers (SHPs), hyperbranched poly(glycidyl methacrylate)s (HPGMAs), were synthesized via reversible addition–fragmentation chain transfer self-condensing vinyl polymerization (RAFT-SCVP). HPGMAs were efficiently functionalized on the whole scaffold via a collection of click chemistries, including the azidation of oxirane, thiol–epoxy click chemistry, thiol–ene click chemistry, copper-catalyzed azide–alkyne cycloaddition (CuAAC), and Menschutkin chemistry, affording SHPs with hetero-functional groups including hydroxyl + azide, dual hydroxyl, triple hydroxyl, hydroxyl + tertiary amine, hydroxyl + alkene, hydroxyl + carboxyl, alkene + azide, alkyne + azide, hydroxyl + alkyne, dual hydroxyl + alkene etc., all at ∼100% conversion. “Thiol–epoxy + thiol–ene” sequential dual click and “thiol–epoxy + Menschutkin chemistry + CuAAC” triple click strategies were presented, making functional group transformation readily accessible. Hydrophilic dendritic brushes, hydrophobic dendritic brushes and amphiphilic dendritic hetero-brushes were synthesized. Esterification of SHP containing hydroxy and azido groups with 1-pyrenebutyric acid yielded clickable fluorescent macromolecules, which showed a very strong excimer emission.