Scalable one-step synthesis of hydroxylated boron nitride nanosheets for obtaining multifunctional polyvinyl alcohol nanocomposite films: Multi-azimuth properties improvement

Introducing hydroxyl (OH) groups onto the surface of chemically inert hexagonal boron nitride (h-BN) is conducive to the exfoliation and functionalization of h-BN, meanwhile could enhance the intermolecular forces with polymer as well. However, chemical inertness generated by partially ionized BN bonds makes the introduction of OH groups still remains a challenge. Here, we reported a scalable one-step thermal calcination method for the fabrication of OH-functionalized h-BN nanosheets (OH-BN). Then, transparent, strong, and flexible as well as flame retardant nanocomposite films of as-prepared OH-BN and PVA were prepared through an aqueous solution casting technique. Due to hydrogen-bond self-assembly and crystalline-region self-relief, elongation at break, tensile strength, and Young's modulus of PVA nanocomposite film were simultaneously increased by 109.3%, 73.6%, and 144.4% with as low as 0.2 wt % OH-BN. Besides, the self-stiffness phenomenon that damages the material elasticity during dynamic service process of PVA nanocomposite films was effectively hindered. Meanwhile, the superior visible light transmittance and higher absorption quality to UV-light were also confirmed, which promoted its practical use in artificial cornea materials. Attributing to the well-dispersed state and layered structure, incorporated OH-BN presented a barrier function to suppress the delivery of thermal degradation products of PVA matrix, thus enhancing thermal stability and fire safety. Herein, we come to a conclusion that the scalable one-step synthesis of OH-BN and environmentally friendly fabrication of PVA/OH-BN nanocomposite films as well as excellent properties greatly contribute to the development of the practical application of h-BN nanosheets, thus obtaining multifunctional composite materials.