2-(dimethylamino)ethyl methacrylate (DMA) was block copolymerized in turn with three other tertiary amine methacrylate comonomers, namely 2-(diethylamino)ethyl methacrylate (DEA), 2-(diisopropylamino)ethyl methacrylate (DPA) and 2-(N-morpholino)ethyl methacrylate (MEMA), using group transfer polymerization (GTP). The DMA residues of each of these diblock copolymers were selectively betainized using 1,3-propane sultone under mild conditions to yield a series of novel betaine diblock copolymers. These selectively betainized copolymers could be dissolved molecularly without co-solvents in aqueous media at room temperature, with micellization occurring reversibly on judicious adjustment of the solution pH, temperature or electrolyte concentration. In all three cases, stable block copolymer micelles were formed with betainized-DMA coronas and hydrodynamic diameters of 10-46 nm. The selective betainization of the DMA residues dramatically reduces the surface activity and increase the solubility of the tertiary amine methacrylate block copolymers (DMA-DEA, DMA-DPA and DMA-MEMA). (C) 2003 Elsevier Ltd. All rights reserved.