Synthesis, Structure, and Properties of MXene-Enhanced Polyurethane Containing Urea Bonds

To overcome the typical limitations of conventional polyurethanes, including insufficient thermal stability, mechanical strength, and recyclability, this study presents a high-performance and reprocessable poly(urethane-urea) nanocomposite reinforced with Ti₃C₂T_x MXene (MX-AHPU). The formation of strong hydrogen bonds between the urea groups of the polymer and the oxygen-functionalized MXene surface was confirmed by FTIR, XRD, and XPS, which also verified the complete reaction of -NCO groups. MXene incorporation substantially improved thermal stability, as evidenced by TGA showing a higher onset decomposition temperature and increased char residue. DSC analysis indicated a raised glass transition temperature, reflecting restricted chain mobility. The composite demonstrated remarkable mechanical enhancement, with tensile strength increasing by 70% to 26.7 MPa and toughness rising by 28% to 311.8 MJ·m^-3, while maintaining exceptional elongation (>3600%). Dynamic mechanical analysis revealed a lower activation energy for stress relaxation (26.6 kJ/mol for MX-AHPU, 30.9 kJ/mol for neat AHPU), indicating enhanced molecular mobility and energy dissipation. Importantly, the material exhibited excellent recyclability, retaining most of its mechanical performance after three reprocessing cycles due to the reversible nature of the interfacial hydrogen bonds. This work provides an effective strategy for designing sustainable, high-performance polyurethane-urea composites suitable for demanding applications such as flexible electronics and advanced coatings.