Degradation behaviors of monomethoxy poly(ethylene glycol)-b-poly(epsilon-caprolactone) nanoparticles in aqueous solution

Monomethoxy poly(ethylene glycol)-b-poly(epsilon-caprolactone)(MPEG-b-PCL) diblock copolymers were synthesized via a ring-opening polymerization. The polymeric nanoparticles prepared by precipitation/solvent evaporation exhibit a core-shell structure, characterized by dynamic light scattering (DLS), nuclear magnetic resonance (NMR), and atomic force microscopy (AFM). The hydrolytic degradation of those nanoparticles was studied by DLS, NMR, and gel permeation chromatography (GPC). It was found that the molecular weight of PCL block in a copolymer significantly affects the stability of nanoparticles in aqueous solution and nanoparticles with shorter PCL block length degraded faster. The degradation behaviors could be divided into two stages with slow degradation at the interface region via swelling effect and fast degradation at inner core via caves and channels formed by cleavage of ester bonds. Copyright (C) 2007 John Wiley & Sons, Ltd.