Effects of Chain Microstructure and Monomer Content on the Degradation Behavior of Levulinic Acid-Based Copolyesters

In this study, fully bio-based poly(glycerol levulinate-co-glycerol malonate) (PGLGM) and poly(glycerol levulinate-co-propylene malonate) (PGLPM) random/block copolyesters were synthesized from glycerol, 1,3-propanediol (PDO), levulinic acid (LA), and malonic acid (MA) via melt polycondensation. These copolyesters were designed for potential biomedical applications, where controlled degradation and optimized material performance are essential. The influence of chain microstructure and monomer content on the in vitro degradation properties of the copolyesters was investigated. Results showed that an increase in MA content in PGLGM copolyesters slowed degradation, with the 40/60 LA/MA ratio retaining 37.18% of its original mass after 8 weeks, whereas the 80/20 ratio retained 37.89% in only 1 week. In contrast, neat PGM degraded faster, with a mass retention of 47.29%. The introduction of PDO in PGLPM copolyesters accelerated degradation, with the 3-block PGLPM retaining 71.17% of its mass after 8 weeks, compared to 49.74% for the random copolymer. Furthermore, a strong linear relationship between water uptake and mass loss was observed, suggesting that water absorption plasticized the copolymer, enhancing chain mobility and hydrolytic degradation. pH changes in the immersion solutions were consistent with the mass loss trends, with pH values falling below 7.0 after 7 days, further supporting the degradation process. These findings highlight the potential for tailoring the degradation behavior of PGLGM and PGLPM copolyesters through the manipulation of copolymer composition and structure, providing opportunities for customizable, environmentally friendly biomedical applications where controlled biodegradability is critical.