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

Abstract

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-PEO113: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.