Highly efficient synthesis of polymer brushes with PEO and PCL as side chains via click chemistry

We reported that well-defined polymer brushes could be prepared efficiently via the grafting-onto approach and the polymer brushes grafted with poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL) and mixed PEO/PCL have been obtained. Firstly, poly(glycidyl methacrylate)s, PG₁₀₀ and PG₉₄₀, were prepared by controlled radical polymerization and their epoxy groups were reacted with sodium azide to introduce azido groups quantitatively. Then the PG derivatives bearing azido groups, poly(3-azido-2-hydroxypropyl methacrylate)₁₀₀ (PGA₁₀₀), were reacted with the alkynyl terminated either PEO (ay-PEO₁₁₃) or PCL (ay-PCL₁₇) through copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction under mild temperature. At a molar feed ratio of ay-PEO ₁₁₃:azido unit = 1:1, the coupling reaction with ay-PEO₁₁₃ proceeded nearly quantitatively. At the same feed, the conversion of grafting ay-PCL₁₇ dropped to ca. 80%. Amphiphilic polymer brushes with randomly grafted PEO and PCL branches were also obtained by feeding the mixed ay-PEO and ay-PCL during CuAAC. By coupling ay-PEO₁₁₃ onto a long backbone PGA₉₄₀, wormlike PEO brushes with an average length of 140 nm were prepared as demonstrated by AFM. This molecular worm was further labeled with Rhodamine B and then was incubated with liver cancer cells HepG2. Preliminary results indicated that the wormlike brushes could be internalized by the cells easily, suggesting the potential application as advanced vehicles for delivery.