We report a methodology for the synthesis of N epsilon-phenoxycarbonyl-protected poly(l-lysine) on the side chain by chain growth polycondensation of N alpha,N epsilon-bis(phenoxycarbonyl)-l-lysine proceeded through the selective elimination of phenol and CO2 from the N alpha phenoxycarbonyl moiety at 50 degrees C in N,N-dimethylacetamide in the presence of a primary amine used as an initiator. After optimization of reaction condition, the addition of acetic acid during polycondensation proved effective for the realization of the predicted molecular weight and narrow dispersity of the corresponding polypeptide by adjusting the feed ratio of monomer to the amine initiator because of the suppression of interchain coupling that occurs between the amino terminus of poly(l-lysine) and the N epsilon-phenoxycarbonyl group on the polymer side chains. Furthermore, taking advantage of the potentially reactive N epsilon-phenoxycarbonyl moiety on the side chain, post-polymerization modification was effectively achieved by the nucleophilic reaction of amine compounds including primary, secondary, and aromatic amines through the formation of urea linkage, providing a useful platform for synthesis of selective side chain functionalization of poly(l-lysine) samples. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2522-2530