Nanoscale dispersion of maltooligosaccharides in poly(ε-caprolactone) for an enhanced mechanical performance and marine-biodegradability characteristics

Marine plastic pollution poses a serious threat to ecosystems and human health. Although poly(ε-caprolactone) (PCL) represents a promising marine-degradable polymer, its poor mechanical properties limit its application. In this study, a new strategy was developed to enhance the mechanical performance of PCL, while maintaining its marine biodegradability. This was based on the incorporation of sugar-based block copolymers (BCPs) as additives. AB- and ABA-type BCPs composed of maltooligosaccharide (Mal_n) as the A block and PCL as the B block were synthesized via copper-catalyzed azide-alkyne click chemistry. Binary blends of PCL with the BCPs or Mal_n were prepared by solvent casting. Mechanical testing revealed that all PCL/BCP blends exhibited improved Young’s moduli and yield strengths compared with the neat-PCL. This was attributed to the nanoscale dispersion of the hard sugar domain as a filler within the PCL matrix. The ABA-type BCP blends achieved an elongation at break of 726% and a stress at break of 24.5 MPa, surpassing the performance of the neat-PCL, whereas the AB-type blends demonstrated lower stretchabilities. The enhancements observed for the ABA-type BCP blends were attributed to the loop and bridge conformations adopted by the PCL chains in the BCPs. The marine biodegradability characteristics were subsequently assessed under simulated seawater conditions. Optical/electron microscopy and mass retention measurements confirmed that Mal_n and BCP addition significantly accelerated biodegradation of the PCL films. These findings demonstrate that sugar-based BCP blending offers a promising approach for balancing mechanical robustness and environmental degradability, providing valuable insights for designing sustainable polymer materials.