Synthesis of Bio-Based PBSeDi Copolyesters: Effect of Disulfide Bond Incorporation on Barrier Properties and...

Environmental concerns regarding petroleum-based plastics have increased demand for biobased materials with tailored properties. In this study, we incorporated a disulfide-containing comonomer, 3,3'-dithiodipropionic acid (Di), into poly-(butylene sebacate) (PBSe) at various molar ratios to synthesize novel poly-(butylene sebacate-co-dithiodipropionate) (PBSeDi) copolyesters with high average molecular weights. Increasing Di content reduced crystallinity and melting temperatures of the copolyesters, and increased glass transition temperatures. Mechanical testing indicated that moderate Di content preserved flexibility, although it reduced tensile strength of PBSeDi. Compared with PBSe, up to 10 mol % Di incorporation decreased oxygen and water vapor permeabilities by 22.7% and 33.1%, respectively, likely due to reduced segmental mobility and free volume associated with the disulfide segments. Under home-composting conditions, weight loss increased with increasing Di content, owing to increased hydrophilicity and lower crystallinity of PBSeDi. Therefore, PBSeDi copolyesters balance thermal processability, barrier performance, and environmental degradability, showing potential for sustainable food packaging applications.