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

Abstract

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(<i>tert</i>-butyl acrylate) (P<i>t</i>BA-N₃) side chains, PBIEM-<i>g</i>-(P<i>t</i>BA-N₃), were prepared by atom transfer radical polymerization (ATRP) of <i>t</i>BA 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 (G<i>n</i>) were introduced onto the brush-shaped P<i>t</i>BA-N₃ by copper-catalyzed azide–alkyne cycloaddition (CuAAC) coupling reaction. The efficiency of CuAAC between P<i>t</i>BA-N₃ side chains and G<i>n</i> has showed a dependence on generation number <i>n</i> of the dendrons. At the feed ratio of [G<i>n</i>]:[N₃] = 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