Nacre-Inspired\nSustainable Polylactide/Poly(butylene\nadipate-<i>co</i>-terephthalate) Blends with an Excellent\nStrength–Toughness Balance

Nacre-inspired sustainable blends,\nin which polylactide (PLA) and\npoly(butylene adipate-<i>co</i>-terephthalate) (PBAT) are\nalternately stacked in parallel, were fabricated by layer-assembly\ncoextrusion. The interfacial diffusion controlled by the layer number\nwas found to play a crucial role in optimizing the mechanical properties.\nWith a poor interfacial diffusion at the layer number ≤32,\nthe weak adhesion between incompatible PLA and PBAT induced multiple\nlayer debonding and stepwise breaking during stretching, leading to\na discount on the advantages of this nacre-inspired structure in integrating\nstrength and ductility. As the layer number exceeded 128h*, the stronger\ninterfacial diffusion triggered the formation of a thin interphase\nlayer, which acted like an amphiphilic physical compatibilizer to\nbind the adjacent layers. This significantly perfected the nacre-inspired\nstructure in PLA/PBAT blends, bringing a dramatic increase in fracture\nstrain to 459.7% while maintaining the strength near 30.0 MPa. Moreover,\nthe interfacial diffusion was systematically analyzed with versatile\nqualitative and quantitative methods, and the diffusion mechanism\nrelated to the extension–compression coupled field in coextrusion\nwas discussed. This work provides a simple strategy for developing\nnacre-like structural materials with an excellent strength–toughness\nbalance, which shows the scalability of various polymer pairs.