Polyoxometalate-based supramolecular star polymers, where an anionic polyoxometalate is closely encapsulated by a hydrophobic shell of cation terminated polystyrenes, are conceptually regarded as a model of star polymers to study their intra- and inter-star interactions and self-assembled behaviors in solvents of variable quality. These model stars can self-assemble to form unilamellar free-standing sheets in the toluene/methanol mixture solvent with a methanol volume ratio of 50%. An increase in the methanol content to 75 or 80% results in a coexistence of free-standing sheets with vesicles, where several intermediates are captured for the morphological evolution from sheet to vesicle. With further increasing methanol content to 90%, pure vesicle phases form with unilamellar or oligo-lamellar features. All these aggregates are packed by the totally hydrophobic star-like polymers, where the core-shell structures are retained. This is distinctly different from the bilayered nanostructures formed by amphiphiles such as surfactants and block copolymers in selective solvents.