Synthesis of High-Strength TPU/MXene Nanocomposites via an In Situ Polymerization Method

Recognizing that interfacial adhesion plays a key role in determining the mechanical properties of nanocomposites, we attempted to synthesize thermoplastic polyurethane (TPU)/MXene nanocomposites with covalently bonded TPU chains on the surfaces of MXene nanosheets through an in situ polymerization method. Different analyses showed that some TPU chains start to grow from the MXene surfaces, leading to significant improvements in the mechanical properties of the TPU/MXene nanocomposites compared to neat TPU and a solution-mixed TPU/MXene nanocomposite. In particular, the in situ synthesized TPU/MXene nanocomposite exhibited a 55% higher elastic modulus and approximately 110% higher tensile strength than neat TPU, as well as a 30% higher elastic modulus and approximately 180% higher tensile strength than the solution-mixed TPU/MXene nanocomposite with the same MXene content (0.5 wt %). This simultaneous improvement in the stiffness and toughness of the materials demonstrates that the in situ synthesis of TPU/MXene nanocomposites, without any surface treatments of the MXene, is a versatile and highly efficient method for reinforcing TPUs. Furthermore, the results indicated that the resulting nanocomposites are not cross-linked and undergo a facile stress relaxation process, making them suitable for commercial processing technologies. To the best of our knowledge, this is the first work on covalent bonding of TPU chains on the surface of MXene nanosheets without pretreatment of MXene surfaces.