Fabricating polylactic acid-based blend composite with balanced stiffness−toughness and excellent shape memory performance by incorporating surface-modified carbon nanofibers

Efficiently designing the interfacial interaction between nanoparticles and components of the blends to achieve the controllable microstructure evolution and resultant performances is still greatly challenging. This work reports the modification of the carbon nanofibers (CNFs) through different strategies. The CNFs before and after being modified were introduced into poly(L-lactic acid)/thermoplastic polyurethane (PLLA/TPU) blend. It is found that the pristine CNFs exhibit little toughening effect on the blend due to the poor interfacial interaction between pristine CNFs and the components of the blends. Hydrogen bonding interaction is formed between the hydroxylated CNFs and the components of the blends, which induces the morphological transition from the sea-island structure to the co-continuous structure, resulting in the improvement of the fracture toughness of the blend to a certain extent. While the epoxidized CNFs simultaneously exhibit the covalent bonding interactions with the two components of the blend and consequently, the epoxidized CNFs play a role in compatibilization, resulting in the blend with high fracture toughness. In addition, compared with the pristine CNFs, modified CNFs endow the blend with more outstanding light-induced mechanical-damage-healing behaviors and shape memory performances. This work not only reveals the influence mechanisms of the interfacial interaction between CNFs and the components of the blend on the microstructure and macroscopic properties of the PLLA/TPU blend, but also provides an effective way for the preparation of the PLLA-based blend composites with structural-functional integration