Synthesis of a Hierarchically Branched Dendritic Polymer Possessing Multiple Dendrons on a Dendrimer-like Backbone

We hereby report the synthesis of a novel type of dendritic structure, a hierarchically branched dendritic polymer, in which discrete dendrons are built at the branch points of a dendrimer-like skeleton. The synthesis consists of two stages, i.e., the preparation of dendrimer-like polystyrene through anionic polymerization and a chlorosilane coupling reaction as well as the formation of carbonate-containing dendrons from the primary hydroxy groups at the branch points of dendrimer-like polystyrene through highly selective reactions between imidazole carboxylic esters and primary hydroxyls. The hydroxy group is introduced by monoaddition of a 1,1-diphenylethylene derivative possessing −OSiBuMe2 during anionic polymerization followed by deprotection. A hierarchically branched dendritic polymer, G3-g3, containing 21 carbonate-derived dendrons and 167 (theoretically 232) hydroxyl groups (subsequently transformed into acetoxy groups for better solubility), in a single dendrimer-like polystyrene, is prepared and characterized by NMR monitoring the synthetic process. The ultimate product shows higher multiplicity of functional groups owing to the high-level dendritic or multiple dendrons on dendrimer-like structure.