Novel poly(butylene succinate-co-lactic acid) copolyesters: Synthesis, crystallization, and enzymatic degradation

A series of aliphatic biodegradable poly(butylene succinate-co-dl-lactide) (PBSLA) copolyesters were synthesized with the aim of improving the degradation rate of poly(butylene succinate) (PBS) by incorporation of dl-oligo(lactic acid) (OLA) into the PBS molecular chains. The composition and sequential structure of the aliphatic copolyesters were investigated by proton nuclear magnetic resonance (¹H NMR) spectroscopy. The crystallization behaviors, the crystal structure and morphology of the copolyesters were investigated by using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and polarizing optical microscopy (POM), respectively. The results indicate that the crystallization of the copolyesters was restricted by the incorporation of lactide (LA) units, which further tuned the mechanical properties of the copolyesters. The copolyesters could form complete spherulites and exhibit the same crystal structure as that of PBS. Enzymatic study indicated that the copolyesters with higher content of LA units degraded faster, and the degradation began in the amorphous regions and then in the crystalline regions. The morphology and the resulting degradation products of the copolyesters were investigated by scanning electron microscopy (SEM) and ¹H NMR analysis during the degradation process.