ACS Sustainable Chemistry & Engineering, 2017, vol 5, 4, pp. 3063-3073
Achieving balanced mechanical performances in a polymer material has long been attractive, but it is still a significant challenge. Herein, a nonadditive strategy was proposed by tailoring the crystalline structure of neat polylactide (PLA) through a layer-multiplying extrusion. Compared with normal PLA, the layer-multiplied material exhibited a 50% increase in tensile strength, a 4-fold improvement in elongation at break, and greatly enhanced resistance to heat distortion. To comprehensively understand the origin of the balanced performances, we carefully observed and analyzed the tailored crystalline structure. It was demonstrated that the multilayer-assembled shish-kebab structure was fabricated because of the iterative extensional and laminating effects occurring in the layer-multiplying process. Inspired by that process in nacres, the layer-packed shish-kebab skeleton was regarded as the strong phase possessing the ability to offer sufficient strength for resisting mechanical and thermal deformation. Meanwhile, the tenacious interfaces played a significant role in crack deflection and termination in achieving high ductility. More significantly, because no external additives are required, the layer-multiplied PLA is capable of maintaining high transparency as well as good biodegradability and biocompatibility, which gives it competitive advantages in packaging, biomedical, and tissue engineering applications.