Use of ionic liquids as reaction media was investigated in the design of an environmentally friendly single electron transfer-living radical polymerization (SET-LRP) for acrylonitrile (AN) without any ligand by using Fe(0) wire as catalyst and 2-bromopropionitrile as initiator. 1-Methylimidazolium acetate ([mim][AT]), 1-methylimidazolium propionate ([mim][PT]), and 1-methylimidazolium valerate ([mim][VT]) were applied in this study. First-order kinetics of polymerization with respect to the monomer concentration, linear increase of the molecular weight, and narrow polydispersity with monomer conversion showed the controlled/living radical polymerization characters. The sequence of the apparent polymerization rate constant of SET-LRP of AN was kapp ([mim][AT]) > kapp ([mim][PT]) > kapp ([mim][VT]). The living feature of the polymerization was also confirmed by chain extensions of polyacrylonitrile with methyl methacrylate. All three ionic liquids were recycled and reused and had no obvious effect on the controlled/living nature of SET-LRP of AN. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 609-613, 2012