Assembled MXene Macrostructures for Multifunctional Polymer Nanocomposites

As a thriving family of 2D nanomaterials, early transition metal carbides and carbonitrides (MXenes) are regarded as promising candidates in various applications. To enhance the mechanical robustness and environmental stability of MXenes, research on their polymer-based nanocomposites with improved oxidation and damage tolerance has attracted increasing attention. As a reinforcing and functional filler, MXenes can also endow polymer with desired thermal/electrical properties. Compared to the powder-based direct dispersion, assembling MXene nanosheets into MXene macrostructures (MMs) is proven as an effective strategy to unite with polymer. In particular, performance of the nanocomposites can be readily optimized by manipulating the structure of MMs and their interactions with polymer. In this Review, recent research progress on the MMs/polymer nanocomposites is summarized to provide a systematic understanding of the relationships among structures, fabrication techniques, and performance. Beyond diverse exfoliation methods for synthesizing MXene flakes, special attention is given to the assembly routes to construct mechanically robust macrostructures and hybrid techniques to build various MMs/polymer nanocomposites. Then, their applications in several areas of fundamental research and practical application are discussed, including heat/electrical conduction, electromagnetic shielding, and flexible devices. Finally, the challenges and perspectives are summarized to guide the future exploration for multifunctional MMs/polymer nanocomposites.