Rational design of two-dimensional nanofillers for polymer nanocomposites toward multifunctional applications

Nanocomposites consisting of two-dimensional (2D) nanostructured fillers embedded in a polymer matrix find ample opportunities to design multifunctional materials for new applications stemming from the nanofillers' exceptional properties. Despite similar geometries, different 2D materials such as graphene, hexagonal boron nitrides, MXene, and transition metal dichalcogenides exhibit vastly different electrical, thermal, optical and electromagnetic characteristics, providing an exciting pathway to creating composites with tailored multifunctional properties. The key is to rationally assemble 2D nanostructured fillers in the matrix with controlled multiscale structures so that their unique properties can be translated into the composites. This paper is dedicated to offering an overview of recent advances empowering the development of 2D nanofiller/polymer composites in the context of novel synthesis and assembly techniques, multiscale structural characteristics, multifunctional properties and emergent applications. Special emphasis is placed on identifying the critical relationships between the material parameters, processing conditions, structures created and properties of final products across nano-, micro-, and macroscales. The real-world understanding enables rational design of composites toward multifunctional applications in the emerging fields of flexible electronics, wearable sensors, energy storage, conversion and harvesting.