The relationship between solid-liquid interface interaction and gelling capacity of h-BN 2D material: a rheological study

Diurea modified h-BN nanosheet is a novel kind of 2D gelator that could gel the lubricating oils under the stimulus of ultrasound. Morphological analyzations in previous study confirmed that the ultrasound induced layer-by-layer (LBL) structure of BN gelator is critical for the gelation. However, the elastic response in LBL structure, which is crucial for the formation of a stable gel system, has not been explicitly illustrated yet. The challenge is that the LBL gelator structure is based on 2D material and thus lacks vertical linkage between gelator layers, which is significantly different from the traditional gel systems that generally possess highly crosslinked gelator network. In this work, by investigating the viscoelastic behavior of the BN-based gel via rheometer, it is found the solid-liquid interface interaction, which is regulated by the diurea molecular structure in the BN gelator, is the key factor for triggering the stable elastic response in the LBL structure, and the elasticity mainly originates from the interface interaction induced bending deformation of h-BN 2D material. The findings further elucidate the gelling mechanism of BN gelators and enlighten the structure design of ultrasound-responsive gelator based on 2D materials.