Micellization of a series of amphiphilic quaternized poly(2-(dimethylamino)ethyl methacrylate)-black-poly(methyl methacrylate) (PQDMAEMA-b-PMMA) copolymers has been studied in water. The alkyl halide used for the quaternization of the aminated block has an effect on the solution properties of the diblocks, that have been investigated by dynamic light scattering and surface tension measurements. When a short length alkyl halide is used, the diblock copolymers behave like traditional amphiphiles, whereas their behavior is similar to polysoaps in case of long alkyl halides. The size of the micelles increases when 1-bromopropan-3-ol is substituted for 1-bromopropane in the quaternization reaction. It is, however, independent of the structure of butyl bromide, i.e. n-butyl vs tert-butyl bromide. The solution properties of a star-shaped PQDMAEMA-b-PMMA copolymer have also been studied and compared to the linear counterpart. The starshaped architecture actually prevents the block copolymer to be properly oriented at the air/water interface in agreement with the formation of unimer micelles. (C) 2001 Elsevier Science Ltd. All rights reserved.