Regenerated cellulose film combining high strength and toughness prepared by synergistic plasticization and...

Regenerated cellulose films tend to be brittle, and the addition of plasticizers typically results in a strength-ductility trade-off, where increased ductility comes at the cost of reduced tensile strength. In this work, we overcome this trade-off by tuning the composition and structure of the films, achieving unprecedented mechanical properties that combine high strength and high ductility. In a typical cellulose-glycerol system, increasing glycerol content only slightly improves elongation at break (remaining below 35%), while tensile strength sharply decreases to 40 MPa. However, by incorporating both polyvinyl alcohol (PVA) and glycerol into the cellulose film, elongation at break reaches 60%, though tensile strength remains at 50 MPa. Further enhancement is achieved through a freeze-thaw treatment of the coagulated hydrogel prior to drying into films. Under optimized conditions, the resulting film exhibits a tensile strength of 120 MPa and an elongation at break of 60%, yielding a high toughness of 55 MJ/m³, significantly outperforming all previously reported regenerated cellulose-based films. The larger deformation and higher strength are attributed to a more uniform stress distribution at the nanoscale, enabled by the homogeneous and dense structure of the film. This study provides an effective strategy for designing bio-based films, breaking the traditional strength-ductility trade-off.