Cu(0)-mediated living radical polymerization was first extended to acrylonitrile (AN) to synthesize polyacrylonitrile with a high molecular weight and a low polydispersity index. This was achieved by using Cu(0)/hexamethylated tris(2-amino-ethyl)amine (Me-6-TREN) as the catalyst, 2-bromopropionitrile as the initiator, and dimethyl sulfoxide (DMSO) as the solvent. The reaction was performed under mild reaction conditions at ambient temperature and thus biradical termination reaction was low. The rapid and extensive disproportionation of Cu(I)Br/Me-6-TREN in DMSO/AN supports a mechanism consistent with a single electron transfer-living radical polymerization (SET-LRP) rather than activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). H-1 NMR analysis and chain extension experiment confirm the high chain-end functionality of the resultant polymer. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5439-5445, 2010