Reported here is self-assembly behavior in selective solvent of diblock copolymers with relatively long corona-forming block compared to core-forming block. Three diblock copolymers, poly(ethylene glycol) monomethyl ether-b-poly (methacryloyl-L-leucine methyl ester), also denoted as MPEG-b-PMALM copolymer, were prepared by fixing MPEG block with an average number of repeating units of 115, whereas varying PMALM block with an average number of repeating unit of 44, 23, 9, respectively. Multiple morphologies, such as sphere, cylinder, vesicle, and their coexisted structures from self-assembly of these diblock copolymers in aqueous media by changing block nonselective solvent and initial polymer concentration used in preparation, were demonstrated directly via TEM observation. These results herein might, therefore, demonstrate as an example that a wide range of morphologies can be accessed not only from "crew-cut micelles" but also from "star-micelles" by controlling over preparation strategies. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 364-371, 2010