In this contribution, a versatile approach for the synthesis of functionalized particles for drug delivery is presented, using two nonaggressive standardized procedures. The first procedure considered is the functionalization of an azido-terminated a-norbornenyl poly(ethylene oxide) (PEO) macromonomer with an alkyne-containing active molecule via the copper catalyzed azide alkyne cycloaddition, click type reaction. The functionalized macromonomer is then polymerized by Ring-Opening Metathesis Polymerization (ROMP) in dispersion to form functionalized particles. The second procedure consists in synthesizing particles by ROMP in dispersed media of norbornene with azido-terminated a-norbornenyl PEO macromonomer. The ROMP was initiated by the first generation Grubbs catalyst. Such functionalized core-shell particles have stealthy properties due to their PEO shell and can be viewed as universal nanocarriers on which any alkyne-modified active molecule can be grafted by click chemistry. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013