Tuning Sequence Length to Regulate Both Toughness and Biodegradation Behavior of Poly (butylene succinate-co-butylene adipate)

The extensive use of conventional plastics has resulted in severe environmental pollution, driving increasing interest in biodegradable polyesters that combine excellent performance with complete degradability. Poly (butylene succinate- co -butylene adipate) (PBSA), derived from poly (butylene succinate) (PBS) by incorporating flexible butylene adipate (BA) units, exhibits broad potential in composting, packaging, and agricultural films. In this study, a series of PBSA polyester materials with systematically varied BA unit sequence lengths were prepared by fine-tuning the composition of adipic acid (AA) and succinic acid (SA), aiming to investigate the effect of BA sequence length on the properties of PBSA. The results indicate that as the BA sequence length decreases, the crystal growth orientation of PBSA shifts from (020), (021), and other planes to (111), accompanied by increased interlamellar spacing and reduced crystallinity, these changes significantly accelerate the enzymatic degradation rate. Meanwhile, the shortened BA sequence promotes spherulite growth, which restricts the mobility of molecular chains and consequently leads to decreases in elongation at break and impact strength. Specific data show that after the shortening of the BA sequence, the elongation at break of PBSA decreases from 810% to 350%, the impact strength drops from 307.2 J/m to 211.9 J/m, and the degradation mass loss rate increases from 71.2% to 99.5%. This study confirms that regulating the BA sequence length enables the synergistic control of both mechanical properties and degradation performance of PBSA polyester materials.