Chemoenzymatic Approach toward Heterografted Molecular Bottle Brushes

Heterografted molecular bottle brushes, i.e., poly(glycidol- graft -ε-caprolactone-acetyl)- co -(glycidol- g raft -methyl methacrylate) [P(G- graft -CL AC )- co -(G- graft -MMA)] and poly(glycidol- graft -ε-caprolactone-acetyl)- co -(glycidol- g raft - n -butyl methacrylate) [P(G- graft -CL AC )- co -(G- graft -BMA)] were prepared in two steps starting with a linear polyglycidol. In the first step an approximately 50% homografted polymer poly(glycidol- graft -ε-caprolactone-acetyl)- co -glycidol [P(G- graft -CL AC )- co -G] was obtained via ring-opening polymerization of ε-caprolactone using polyglycidol as a multifunctional macroinitiator and Novozyme 435 (Lipase B from Candida antarctica (CALB) immobilized on a macroporous resin) as a catalyst. Selective acetylation of the hydroxy groups at the graft ends was achieved via enzymatic acetylation with vinyl acetate, and the hydroxy groups at the backbone were acylated with 2-bromo-2-methylpropionyl bromide. Finally poly(methyl methacrylate) or poly( n -butyl methacrylate) grafts were attached by atom transfer radical polymerization. The heterografted molecular bottle brushes show monomodal elution curves in gel permeation chromatographic analyses. Differential scanning calorimetry confirms the existence of phase separated domains for both polymers.