Reversible Sol-Gel Transition of Silicone Complex Oils Using Hydrophobically Modified Attractive Hectorite Nanoplatelets as Rheology Modifiers

Hectorite nanoplatelets (HNPs) have truly intriguing surface properties such as high specific surface area, high cation exchange capacity. Herein, we introduce a facile but robust approach to fabricate attractive hectorite nanoplatelets (AHNPs), in which the surface of HNPs was hydrophobically modified by using a cationic surfactant, dimethyl dioctadecyl ammonium chloride. We could finely disperse the AHNPs in the silicone oil by repeated high pressurized homogenization. The suspension rheological studies revealed that the AHNPs interacted to form a strong gel phase that exhibits the reversible shear stress-responsive sol-gel transition. Based on the chemical and structural characterization of AHNPs by using XRD, FT-IR, AFM, and TEM analyses, we interpreted this is attributed to the weak but long-range edge-to-edge interaction of AHNPs in the silicone oil, which is induced by the hydrogen bonding between small amounts of hydroxy groups at the edge of AHNPs. The AHNPs fabricated in this study are expected to be widely used as rheology modifiers for various oil-based complex fluids.

Keywords: Sol-gel transition, hectorite nanoplatelets, suspension rheology, rheology modifiers