Synthesis of Cylindrical Polymer Brushes with Umbrella-Like Side Chains via a Combination of Grafting-from and Grafting-onto Methods

Cylindrical polymer brushes with umbrella-like side chains have been synthesized by a combination of grafting-from and grafting-onto methods. First, the polymer brushes with azido end-functionalized poly(tert-butyl acrylate) (PtBA-N-3) side chains, PBIEM-g-(PtBA-N-3), were prepared by atom transfer radical polymerization (ATRP) of tBA monomers using polyinitiator PBIEM followed by a substitution of bromo-side terminals with sodium azide. Subsequently, polyamidoamino dendrons of three generations with a propargyl focal point (Gn) were introduced onto the brush-shaped PtBA-N-3 by copper-catalyzed azide-alkyne cycloaddition (CuAAC) coupling reaction. The efficiency of CuAAC between PtBA-N-3 side chains and Gn has showed a dependence on generation number n of the dendrons. At the feed ratio of [Gn]:[N-3] = 1:1, the grafting efficiency of the first generation dendron (G1) reached above 95%, whereas that of G2 and G3 was at least 84% and 73%, respectively. AFM images indicated that diameter of the brushes hybridized with G3 increased obviously than that of the brushes without dendrons.