The Telomerization of methyl methacrylate with 2-aminoethanethiol hydrochloride initiated by 2,2'-azobisisobutyronitrile, was investigated in dimethylformamide (DMF). First, the peculiar behavior of 2-aminoethanethiol was highlighted because it behaves as a peculiar transfer agent; this is because its transfer constant (C-T) is weak compared with that of other thiols. The presence of the amine function greatly disturbs the free radical telomerization reaction. Telomerization was performed in the presence of hydrochloric acid (HCl) to protect the amine group. The transfer constant was strongly influenced by the acid and water concentration. This work emphasized that the nature of the solvent plays an important role in the determination of the transfer constant. Thus, the value of CT increased from 0.23 in DMF to 0.56 in the HCl/DMF mixture. The primary and secondary amines were recovered after the reaction. The functionality of the primary and secondary amines was measured by titration. The influence of the concentration of HCl on the resulting amine functionality was investigated. The acid presence prevents the formation of secondary amines, arising from Michael's reaction, on methyl methacrylate. Finally, these results were applied to the synthesis of amine-functionalized telomers with molecular masses of 2000 to 15,000 g/mol. The amine function was correlated with the decrease of R-0 ([telogen]/[monomer]). (C) 2004 Wiley Periodicals, Inc.