We report on the micellization behavior of tri- and tetrablock copoly(2-oxazoline)s in water-ethanol mixtures. The copolymers are based on different combinations of 2-methyl-, 2-ethyl-, 2-phenyl-, and 2-nonyl-2-oxazoline. The solvophilic/solvophobic balance of these copolymers can be tuned thanks to the solubility dependence of the poly(2-phenyl-2-oxazoline) block on the solvent composition. Characterization of the obtained micelles by dynamic light scattering and transmission electron microscopy revealed that their size and morphology depend on the solvophobic content of the copolymers and on the block order. Spherical micelles are always obtained when poly(2-nonyl-2-oxazoline) is the only solvophobic block. When the solvophobic fraction consists of both the poly(2-phenyl-2oxazoline) and poly(2-nonyl-2-oxazoline) blocks, spherical and cylindrical micelles as well as vesicles have been observed. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3095-3102, 2010