A series of poly(2-vinylpyridine)-block-poly (dimethylamino)ethyl methaerylate) diblock copolymers (P2VP-b-PDMAEKA) have been synthesized by living anionic polymerization of the comonomers. Dynamic light scattering (DLS) has been used to study the associative behavior of these copolymers in water as a function of copolymer composition, pH, ionic strength, and temperature. Three association regimes are observed. At low pH, loose aggregates are formed, although both the P2VP and PDMAEMA blocks are protonated. At intermediate pH, micelles are observed that consist of an uncharged hydrophobic P2VP core surrounded by a protonated PDMAEMA corona. At higher pH, the PDMAEDA corona is essentially uncharged and collapses at temperatures higher than 40 degreesC, which results in unstable micelles. The micelles observed by transmission electron microscopy are spherical.