Fabrication of attractive hectorite nanoplatelets by high-pressure homogenization for shear-responsive reversible rheology modification of organogels

Abstract

Hectorite nanoplatelets (HNPs) have intriguing surface properties such as high specific surface areas and high cation exchange capacities. Here, we introduce a facile but robust approach to fabricate attractive hectorite nanoplatelets (AHNPs), in which the surfaces of HNPs were hydrophobically modified by using a cationic surfactant, dimethyldioctadecylammonium chloride. The chemical and structural characterization, performed by X-ray diffraction, Fourier transform infrared spectroscopy, confocal laser scanning microscopy, and transmission electron microscopy, revealed that the edge of AHNPs was richly functionalized with hydroxy groups. We then prepared the organogels by finely dispersing the AHNPs in the silicone oil by repeated high-pressure homogenization. Suspension rheology studies suggested that the interaction between AHNPs led to the formation of a strong gel phase, which exhibited a reversible sol-gel transition in response to the applied shear stress. This was attributed to the weak, but long-ranged interaction between AHNPs in the silicone oil, which were induced by hydrogen bonding between the few hydroxyl groups that are present at the edges of the AHNPs. The AHNPs fabricated in this study are expected to be widely used as rheology modifiers in various oil-based complex fluids.