The first example of well-controlled atom transfer radical polymerization (ATRP) of a permanently charged anionic acrylamide monomer is reported. ATRP of sodium 2-acrylamido-2-methylpropanesulfonate (NaAMPS) was achieved with ethyl 2-chloropropionate (ECP) as an initiator and the CUCl/CUCl2/tris(2-dimethylaminoethyl)amine (Me6TREN) catalytic system. The polymerizations were carried out in 50:50 (v/v) N,N-dimethylformamide (DMF)/water mixtures at 20 C. Linear first-order kinetic plots up to a 92% conversion for a target degree of polymerization of 50 were obtained with [ECP]/[CUCl]/[CUCl2]/[Me6TREN] = 1:1:1:2 and [AMPS] = 1 M. The molecular weight increased linearly with the conversion in good agreement with the theoretical values, and the polydispersities decreased with increasing conversion, reaching a lower limit of 1.11. The living character of the polymerization was confirmed by chain-extension experiments. Block copolymers with N N-dimethylacrylamide and N-isopropylacrylamide were also prepared. The use of a DMF/water mixed solvent should make possible the synthesis of new amphiphilic ionic block copolymers without the use of protecting group chemistry. (c) 2005 Wiley Periodicals, Inc.