Ring-opening copolymerization (ROCP) of L-lactide (L-LA) and (3S)-benzyloxymethyl-(6S)-methyl-morpholine-2,5-dione [(3S, 6S)-BMMD] initiated by creatinine acetate, a biogenic organic compound, was performed in the bulk at 130 degrees C. The copolymerization was well controlled as evidenced by that both the measured values of number-average molecular weight (Mn,NMR(OH) and Mn,NMR(COOH)) and serine molar fraction (FBz.ser) of synthesized copolymers were close to the corresponding theoretical values; and that the higher isotacticity of synthesized copolymers (8586%) and lower racemization degree of the ROCP. After removing O-benzyls of the copolymers with Et3SiH/Et3N/CH2Cl2 under catalysis of PdCl2, functional biodegradable copolymers of L-lactic acid (L-Lac) and L-Ser with designed molar fraction of serine (Fser 1.35%, 3.57%, 5.41%), narrow molecular weight distribution (polydispersity index 1.101.36), and improved hydrophilicity (theta stat 82.389.6 degrees) were finally obtained. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012