The phase diagrams of nanoparticles based on self-assembled amphiphilic poly( 1,2-butadiene)-b-poly(ethylene oxide) diblock copolymers (PB-b-PEO) and subsequent intra-micellar cross-linking in methanol and water show that the obtained morphology of the nanoparticles depends on: (i) the block ratio; (ii) the block length; (iii) the solvent; and (iv) the PEO-sided end group. Depending on these parameters, spherical, cylindrical and vesicle-like nanoparticles are synthesized. The PEO-sided end group is found to have an influence on the morphology of the nanoparticles and in addition, it has an impact on the characteristic dimension of the polymeric nanoparticles. (c) 2005 Elsevier Ltd. All rights reserved.