Amphiphilic diblock copolymer polycaprolactone-block-poly(glycidyl methacrylate) (PCL-b-PGMA) was synthesized via enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). Methanol first initiated eROP of F-caprolactone (F-CL) in the presence of biocatalyst Novozyme-435 under anhydrous conditions. The resulting monohydroxyl-terminated polycaprolactone (PCLOH) was subsequently converted to a bromine-ended macroinitiator (PCL-Br) for ATRP by esterification with alpha-bromopropionyl bromide. PCL-b-PGMA diblock copolymers were synthesized in a subsequent ATRP of glycidyl methacrylate (GMA). A kinetic analysis of ATRP indicated a living/controlled radical process. The macromolecular structures were characterized for PCL-OH, PCL-Br, and the block copolymers by means of nuclear magnetic resonance, gel permeation chromatography, and infrared spectroscopy. Differential scanning calorimetry and wide-angle X-ray diffraction analyses indicated that the copolymer composition (epsilon-CL/GMA) had a great influence on the thermal properties. The well-defined, amphiphilic diblock copolymer PCL-b-PGMA self-assembled into nanoscale micelles in aqueous solutions, as investigated by dynamic light scattering and transmission electron microscopy. (c) 2007 Wiley Periodicals, Inc.