Poly(ethylene oxide) monomethylether was functionalized by alkyl chains of various lengths (l = 10-19 methylene groups) bearing a polymerizable methacrylate moiety. Each synthesis step on the polymer gives quantitative functionalization rates. The self-assembly of the amphiphilic polymers in water was studied by light scattering for various end-groups. Sterical and polar effects were shown to influence the micellization step. The cores of the micelles formed by PEO-C-1-methacrylate were irreversibly cross-linked by UV irradiation. Star polymers that are stable under dilution in good solvent are obtained after 1-min irradiation. The hydrodynamic radius and the molar mass of the nanoparticles depend on the amount of photoinitiator introduced in the cores. (c) 2005 Elsevier Ltd. All rights reserved.