A novel strategy to construct co-continuous PLA/NBR thermoplastic vulcanizates: Metal-ligand coordination-induced dynamic vulcanization, balanced stiffness-toughness and shape memory effect

In the field of dynamic vulcanization, irreversible covalent bonds are utilized to fabricate thermoplastic vulcanizates (TPVs) generally. In this work, a new strategy, metal-ligand coordination-induced dynamic vulcanization, is presented to design polylactide (PLA)/butadiene acrylonitrile rubber (NBR)/cupric sulfate (CuSO4) TPVs with balanced stiffness-toughness and shape memory property. During dynamic vulcanization, the micron-sized CuSO4 particles have been transformed into nanoparticles by the process of dissolution-reaction-redissolution-reaction and then distributed in the continuous NBR phase. CuSO4 nanoparticles cross-link NBR through the coordination interaction between nitrile groups and copper ions, and simultaneously reinforce the NBR phase. This endows the TPVs with balanced stiffness-toughness properties: notched Izod impact strength of 152.88 kJ/m(2) and tensile strength of 22.30 MPa. Furthermore, the fabricated TPVs exhibit co-continuous morphology which resulted in excellent shape memory effect of obtaining shape recovery ratio of 92.30%. We present a novel approach to toughen and enhance PLA-based shape memory materials simultaneously, and it may expand the research scope of dynamic vulcanization.