Synthesis of Novel Amphiphilic and pH-Sensitive ABC Miktoarm Star Terpolymers

Abstract

Novel amphiphilic ABC miktoarm star terpolymers were synthesized that consist of hydrophilic poly(ethylene oxide) (PEO), hydrophobic poly(ε-caprolactone) (PCL), and pH-sensitive poly(2-vinylpyridine) (P2VP), thus a water-soluble block upon protonation. In the first step, poly(ethylene oxide monomethyl ether) (MPEO) was capped by one ω-epoxy end group by reaction of the original hydroxy end group with epichlorohydrin. MPEO-b-P2VP diblock copolymers were prepared by nucleophilic addition of living P2VP-Li+ chains onto the epoxy group of MPEO's. Finally, the hydroxy group formed at the junction of the MPEO and P2VP blocks was used to initiate the ring-opening polymerization of ε-caprolactone in the presence of tin octoate. The ABC star-shaped triblocks were characterized by 1H NMR spectroscopy and size exclusion chromatography.