Well-defined epoxy functionalized four-armed star diblock copolymers were synthesized by atom transfer radical polymerization (ATRP) using the "core-first" approach. In accordance with this synthetic methodology, in a first step, bromine-terminated four-armed star homopolymers of styrene (S) and methyl methacrylate (MMA) were prepared. Then, in a second step, the S[PS-Br](4) and S[PMMA-Br](4) samples were employed as macroinitiators in the ATRP of an oxirane functionalized monomer, like glycidyl methacrylate (GMA). These copolymerization reactions were carried out in benzonitrile solution, at relative-low polymerization temperature, 50 degrees C, and using copper chloride with N,N,N',N,N-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. Linear first-order kinetics with respect to the [GMA](0) were observed, and the analyses of the copolymers obtained by means of size exclusion chromatography (SEC) and H-1 nuclear magnetic resonance spectroscopy (H-1 NMR) demonstrated the high degree of control achieved in the copolymerizations. Moreover, their crosslinkable capacity was studied with a linear diamine by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), indicating their clear potential for epoxy resins technologies. (C) 2008 Elsevier Ltd. All rights reserved.