Toughening of Polylactide with High Tensile Strength via Constructing an Integrative Physical Crosslinking Network Based on Ionic Interactions

Abstract

For polylactide (PLA) toughening modification by rubbery materials, the toughness generally improved at the expense of lowered mechanical strength even after interfacial compatibilization. In this work, an “integration toughening mechanism” was developed for preparing PLA-based materials with simultaneous high strength and high toughness by constructing an integrative physical network throughout both the toughening phase and PLA matrix. A multiblock copolymer containing polycaprolactone (PCL) blocks, PLA blocks, and ionic segments with a random block sequence was prepared and then incorporated with PLA for constructing a physical network based on ionic interactions among copolymers. When subjected to dynamic impact stress, the yield and plastic deformation take place in both the PCL toughening phase and the amorphous region of PLA to dissipate impact energy owing to the integrative network, resulting in a high impact toughness of the material (46.5 kJ/m2). Meanwhile, when subjected to static tensile stress, the integrative network effectively inhibited the large-scale deformation of the PCL phase and promoted the whole system including those rigid crystalline regions to resist external stress. Therefore, the toughening-modified PLA exhibited a relatively high tensile strength (72 MPa) comparable to that of neat PLA.