Atom transfer radical polymerization of sodium 2-acrylamido-2-methylpropanesulfonate

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 (AMPS) was achieved by using ethyl 2-chloropropionate (ECP) as initiator and the CuCl/CuCl2/tris(2-dimethylaminoethyl)amine (Me6TREN) catalytic system. The polymerizations were carried out in DMF:water 50:50 (v/v) mixtures at 20 °C. Linear first order kinetic plots up to 92% of conversion for target Xn = 50 were obtained using [ECP]:[CuCl]:[CuCl2]:[Me6TREN] = 1:1:1:2 and [AMPS] = 1 M. Molecular weight increased linearly with conversion in good agreement with the theoretical values and 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 (DMAAM) and N-isopropylacrylamide (NIPAAM) were also prepared. The use of a DMF-water mixed solvent should make possible the synthesis of new amphiphilic ionic block copolymers without using protecting group chemistry.