A series of novel well-defined dimethylsiloxane-2-(dimethylamino)ethyl methacrylate diblock and triblock copolymers mere synthesized in various solvents at or above ambient temperature. This was achieved by the oxyanion-initiated polymerization of 2-(dimethylamino)ethyl methacrylate (DMA) using either monofunctional or bifunctional low molecular weight poly(dimethylsiloxane) (PDMS) as macroinitiators. Provided that the terminal hydroxyl groups of the PDMS macroinitiators are carefully titrated to the corresponding potassium alcoholates, reasonably good control over the DMA chain length was achieved. H-1 NMR characterization of these DMS-DMA diblock copolymers proved unexpectedly problematic since micellization generally occurred even in solvents such as CDCl3 or d(8)-toluene, which are good solvents for both DMS and DMA homopolymers. Electron microscopy and dynamic light scattering studies confirmed the formation of spherical, polydisperse micelles of 200 nm. Presumably micellization is driven by a demixing term: the PDMS block prefers to be less solvated in order to avoid interacting with the DMA residues. Reliable block compositions were eventually obtained by NMR analysis of dilute solutions of the diblock copolymers in 3:1 d(8)-IPA-D2O mixtures. These DMS-DMA diblock copolymers were highly surface active, particularly at pH 9 where the degree of protonation of the DMA. block was low. Dynamic light scattering studies indicated micellization in aqueous solution, as expected.