Effect of Thermal and Mechanical Rejuvenation on a Model Thermoreversible Colloidal Gel

The aging behavior of adhesive hard sphere (AHS) colloidal gels is of interest due to the role of these gels in common pharmaceutical and consumer products. In this work we examine the possibility of shear rejuvenation in an octadecyl-coated silica nanoparticle system, which has previously been shown to exhibit anomalous aging behavior following a thermal quench (Suman and Wagner, The Journal of Chemical Physics 157 (2), 024901 2022). This AHS system is observed in comparison to Pluronic F-127, which is expected to show shear rejuvenation following a thermal quench. We observe the phase transition behavior of Pluronic-F127 and the AHS system, then investigate the behavior of each system following thermal versus shear rejuvenation. Our comparative analysis shows differences in the aging behavior between systems and demonstrates a lack of shear rejuvenation in the AHS system. Our rheological characterization at different amplitudes, temperature ramp rates and pre-shear history shows intriguing effects of non-equilibrium parameters on the kinetics of aging behavior of colloidal gels. This study of phenomenon of aging in model colloidal gel system is of both fundamental importance and industrial relevance in determining the shelf-life of products based on colloidal gels.