Rheological behavior of SiO2 NP/CTAB/PPA wormlike micelles in alcohol/water mixture

Abstract

This study explores the effect of alcohol on the rheological behavior of SiO₂ nanoparticle (NP) in cetyltrimethylammonium bromide (CTAB)/potassium hydrogen phthalate (PPA) wormlike micelles (WLMs). No previous literature explored the effect of chemical stresses on NP-mediated WLMs. The addition of 0.05 wt% NPs increased the zero-shear viscosity of 30 mM CTAB/20 mM PPA WLMs by 30%. A further increase in SiO₂ NPs disrupted the micellar structure, resulting in reduced viscosity. The optimum SiO₂ NP content increased from ~ 0.05 wt% to ~ 0.4 wt% as the CTAB and PPA concentrations increased from 30 mM CTAB/20 mM PPA to 90 mM CTAB/60 mM PPA. The effect of ethanol and 1-hexanol on WLMs composed of 0.05 wt% SiO₂ NP/30 mM CTAB/20 mM PPA was assessed. The NPs enhanced the shear viscosity of ethanol/WLM systems. Notably, at ethanol concentrations of 0.14 wt%, 0.60 wt% and 1.40 wt%, the zero-shear viscosity increased by approximately 60%, 100%, and 25%, respectively. SiO₂ NPs acted as junction points, facilitating the crosslinking among shorter micelles and improving micellar entanglement. Conversely, SiO₂ NPs had little impact on 1-hexanol/WLM systems owing to the strong interaction between WLMs and 1-hexanol at the micellar interface.