A new family of biodegradable amino-acid-based poly(ester amide)s (AA-PEAs) and amino-acid-based poly(ether ester amide)s (AA-PEEAs) consisting of reactive pendant functional groups (-COOH or NH2) were synthesized from unsaturated AA-PEAs and AA-PEEAs via a thiol-ene reaction in the presence of a radical initiator (2,2'-azobisisobutyronitrile). The synthetic method was a one-step reaction with near 100% yields under mild reaction conditions. The resulting functional AA-PEA and AA-PEEA polymers were characterized by Fourier transform infrared spectroscopy, NMR, and differential scanning calorimetry. These new functional AA-PEA and AA-PE EA derivatives had lower glass-transition temperatures than the original unsaturated AA-PEA and AA-PEEA polymers, and their solubility in some organic solvents also improved. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3386-3394, 2010