Controlled synthesis of AB2 amphiphilic triarm star-shaped block copolymers by ring-opening polymerization

This paper describes the synthesis of a novel amphiphilic AB(2) triarm star-shaped copolymer with A = non-toxic and biocompatible hydrophilic poly(ethylene oxide) (PEO) and B = biodegradable and hydrophobic poly(epsilon-caprolactone) (PCL). A series of AB(2) triarm star-shaped copolymers with different molecular-weights for the PCL block were successfully synthesized by a three-step procedure. alpha-Methoxy-omega-epoxy-poly(ethylene oxide) (PEO-epoxide) was first synthesized by the nucleophilic substitution of alpha-methoxy-omega-hydroxy-poly(ethylene oxide) (MPEO) on epichlorohydrin. In a second step, the alpha-methoxy-omega,omega'-dihydroxy-poly(ethylene oxide) (PEO(OH)(2)) macroinitiator was prepared by the selective hydrolysis of the omega-epoxy end-group of the PEO-epoxide chain. Finally, PEO(OH)(2) was used as a macroinitiator for the ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon CL) catalyzed by tin octoaote (Sn(Oct)(2)). PEO-epoxide, PEO(OH)(2) and the AB(2) triarm star-shaped copolymers were assessed by H-1 NMR spectroscopy, size exclusion chromatography (SEC) and MALDI-TOR The behavior of the AB(2) triarm star-shaped copolymer in aqueous solution was studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM). (C) 2009 Published by Elsevier Ltd.