Enhancing low-temperature resistant and biodegradation of poly(butylene succinate-co-butylene adipate) foams via chain composition modulation and supercritical CO2 foaming

Biodegradable poly(butylene succinate -co- butylene adipate) (PBSA) was synthesized with varying adipic acid (AA) content via in-situ polymerization to systematically investigate the influence of chain segment composition on molecular structure, mechanical properties, foaming performance, and degradation behavior. Increased AA content enhances molecular chain flexibility, reduces crystallinity from 26.73% to 11.52%, and lowers the glass transition temperature ( T g ) from −37.0 ℃ to −51.2 ℃, thereby broadening the application window of PBSA in low-temperature environments. The incorporation of AA also widens the temperature window of supercritical CO₂ foaming, increasing the toughness and CO₂ solubility and reducing the strength of PBSA. Therefore, moderate incorporation of flexible segments can optimize the foaming properties of PBSA. PBSA foam with 40% AA content (A40) achieves a maximum initial expansion ratio of 55.3 and stable expansion ratio of 21.7. The degradation rate of PBSA foams was enhanced and the low-temperature applicability was broadened with increasing AA content. A40 foam(8 times) demonstrates superior compressibility at −45 ℃ and accelerate biodegradation (achieving 43.9% weight loss in soil within 8 weeks). This work highlights the potential of monomer ratio modulation in biodegradable bio-based polyesters to tailor foam properties for specific environmental and functional requirements, providing critical insights into the development of sustainable cushioning materials with tunable temperature applicability.