A novel ligand, N,N,N',N',N"-penta (methyl acrylate) diethylenetriamine (MA(5)-DETA), was synthesized by the reaction of diethylenetriamine with methyl acrylate in almost quantitive yield. The polymerizations of methyl methacrylate with MA(5)-DETA as the ligand and alpha,alpha-dichlorotoluene (DCT) and ethyl 2-bromoisobutyrate (2-EBiB) as the initiators, respectively, under different conditions were examined. The polymerization with CuCl/MA(5)-DETA/DCT was closely controlled in bulk and gave polymers with quite narrow molecular weight distributions (M-w/M-n's) of 1.16-1.29. The polymerization with the system CuBr/MA(5)-DETA/EBiB in bulk gave high activity. However, the system was not well controlled and gave the polymers with M-w/M-n = 1.35-1.53. The solution polymerization in anisole with CuBr/Ma(5)-DETA/EBiB showed a better-controlled nature. Moreover, the addition of CuBr2 into the aforementioned system can further improve its controllability. The M-w/M-n'S of the resulting polymers ranged from 1.11 to 1.21. (C) 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1963-1969, 2004.