Effect of exfoliation degree on the performance of montmorillonite nanosheets

Montmorillonite (MMT) is easily exfoliated into two-dimensional(2D) nanosheets, which are widely used to prepare functional composites. However, there are few studies on the differences in the performance of MMT nanosheets (MMTNS) with different exfoliation degrees, which seriously limits the further breakthrough in the preparation of high-performance MMTNS based materials. In this work, some representative performance of MMTNS with different exfoliation degrees was investigated, and the performance was closely related with making functional composites. The exfoliation degrees of MMTNS were controlled by different ultrasonic exfoliation powers. The performance of MMTNS was studied by the measurements of atomic force microscopy (AFM), Zeta potential, turbidity, viscosity, scanning electron microscopy (SEM) and molecular dynamics simulation. The results show that MMTNS with high exfoliation degree had more negative electrical sites exposed and stronger repulsive potential energy between particles, which exhibited high surface negative electricity and excellent dispersion stability. Moreover, the MMTNS with high exfoliation degree had better gelling property. It can be seen that the "house-of-cards " structure in the structure after gelation of MMTNS with high exfoliation degree was more intensive. Also, with the increase of MMTNS exfoliation degree, its adsorption capacity for organic matter was better and its reaction with organic was more active. These findings might be helpful to select the suitable MMTNS for making functional composites by controlling its exfoliation degree.