A series of aliphatic biodegradable poly(butylene succinate)-co-oligo(L-valine) (PBSVAL) copolyesters were synthesized with dimethyl succinate, 1,4-butanediol (BDO), and oligo(L-valine) (OVL) as reagents. The GPC results show that the weight average molecular weight (Mw) of the copolyester with a feed ratio (PBS/OVL) of 0.9/0.1 (PBSVAL10) is 4.9 x 10(4) g/mol, and its polydispersity index is 1.68. All the copolyesters were more thermally stable than the pristine poly(butylene succinate) (PBS). The incorporation of valine units into the copolyesters eventually led to the decrease of the crystallization temperature, melting temperature, while increase of crystallization enthalpy and melting enthalpy. The crystal structure of the copolyesters is similar to pure PBS except for higher degrees of crystallinity; also there was a trend to higher degrees of crystallinity with increasing content of valine. From the enzymatic degradation experiment, it is clear that the PBSVAL10 copolyester shows less weight loss as compared to pure PBS which is due to PBSVAL10 with higher degree of crystallinity. The morphology of the copolyester films after degradation was also studied by the scanning electron microscopy. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012