The self-assembly in water of an amphiphilic P(nBMA50%-stat-DMAEMA50%)100-b-PDMAEMA235 diblock copolymer based on hydrophilic dimethylaminoethylmethacrylate (DMAEMA) units and hydrophobic n-butylmethacrylate (nBMA) ones is reported. DMAEMA units have been incorporated into the hydrophobic block of this copolymer to moderate its hydrophobic character. Light scattering experiments revealed the formation of micelles whose apparent aggregation number varied reversibly with the ionization degree of the DMAEMA units. Incorporating hydrophilic units into the hydrophobic block of an amphiphilic block copolymer is thus a way to generate dynamic aggregates in aqueous medium. As this strategy was also successful using other types of hydrophilic units, we believe it to be universal.