Tough, adhesive and self-healing conductive 3D network hydrogel of physically linked functionalized-boron nitride/clay /poly(N-isopropylacrylamide)

Abstract

Superior mechanical properties and self-healing abilities seem contradictory due to their opposite relationship with chain mobility. However, rational design with a suitable material system can tackle it. In this work, we fabricated functionalized-boron nitride nanosheets (f-BNNS) with the assistance of supercritical CO₂ (SC CO₂) for the first time. Subsequently, inspired by natural materials, we utilized the obtained f-BNNS to build a type of physically linked peculiar 3D hierarchical f-BNNS/clay/PNIPAM ternary network (TN) hydrogel by introducing readily reformable non-covalent bonds as cross-linkers and sacrificial bonds. Hence, the hydrogel has a high toughness, adhesiveness, and automatically self-healing ability. The vital innovative point of our material design is the incorporation of f-BNNS with H-grafted nitrogen/OH-grafted boron atoms. On the one hand, embedding 2D hard f-BNNS into a soft polymer network can enhance the mechanical properties through an effective load transfer and dissipated energy via the incorporation of sacrificial non-covalent hydrogen bond; on the other hand, nanoscale f-BNNS will slide under π–π interactions and ample hydrogen bond interactions, which can induce the mobility of the polymer molecular chains, thus endowing the hydrogel with a self-healing ability under mild conditions. What's more, the TN hydrogel is conductive and can act as a superb platform to host diverse nano-building blocks. Without doubt, the as-prepared physically linked hydrogel can be used in various application fields in the future, such as sensors, tissue engineering, flexible devices, etc.