Effects of a Low-Molecular-Weight Gelator in Vegetable, Mineral Oil and Cocoa Butter: A Comparative Rheological Study

The demand for eco-friendly viscosity modifiers in food, cosmetics, and lubricants has increased, promoting the development of high-performance, sustainable materials. Low-molecular-weight gelators (LMWGs) are promising candidates, though their behavior in complex systems remains underexplored. In this study, a novel alkylamido isophthalic acid-based LMWG (AIPA-gallic acid) was synthesized. Its performance was evaluated in vegetable oil, mineral oil, and cocoa butter using rheological measurements across varying concentrations and temperatures, with all dynamic rheological measurements conducted in the viscoelastic region. Cacao butter is solid at 15 °C, so the flow curve that can be obtained at this temperature should show high values not comparable with the other liquid oils. No slippage phenomenon was observed. Using a step-rate protocol before acquiring the flow curves, no time-dependent behavior (thixotropy) was observed. Frequency and flow sweep tests were used to assess viscoelastic properties, interaction strength, and coordination number. Results revealed that incorporating AIPA-gallic acid at 4 wt% increased the viscosity by 74 times (at 25 °C) in mineral oil, compared to an increase of about four orders of magnitude in vegetable oil. This suggests the formation of intermolecular interactions that lead to an increased momentum transport process, which is significantly higher in vegetable oil. In contrast, cocoa butter exhibited minimal rheological changes, suggesting that no gelation occurred. Analysis using the weak gel model confirmed that viscosity enhancement arises from a structured network in mineral and vegetable oils, but not in cocoa butter. Temperature-dependent variations in structural parameters further highlight the role of molecular interactions between the gelator and the oil matrix.