We developed a simple route to prepare stabilized micelles and nanovesicles in aqueous solutions. A hydrophobic poly(succinimide) (PSI) was conjugated with the hydrophilic poly(ethylene glycol) (PEG) as a new type of cross-linkable unit. Spherical aggregates were formed when dissolving the amphiphilic PEG(682)-b-PSI130 copolymer in aqueous solutions directly, and polymer nanovesicles were prepared by a precipitation-dialysis method using PEG(455)-b-PSI130 copolymer. Bifunctional primary amine was added to the micelle or nano-vesicle solutions to prepare cross-linked structures via aminolysis reaction of the succinimide units. The degree of cross-linking was controlled by adjusting the molar ratio of the cross-linker to the succinimide units. Increasing the degree of cross-linking leads to the compaction of the micelle core thus reduced diameter. The cross-linked polymer micelles or nanovesicles maintained their morphology in extremely diluted solutions because of their structural stability. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 203-210, 2011