Rheological behavior and microstructure of AgBr nanoparticle/cetyltrimethylammonium bromide/potassium hydrogen phthalate wormlike micelles

Abstract

The rheological behavior and interaction between in-house prepared AgBr nanoparticles (NPs) and wormlike micelles (WLMs) were explored in this work. The AgBr NPs were synthesized by reacting aqueous AgNO3 with cetyltrimethylammonium bromide (CTAB) in a micellar system containing CTAB and potassium hydrogen phthalate (PPA) hydrotrope. The size, composition, and morphology of the NPs were characterized using dynamic light scattering, transmission electron microscopy (TEM), thermal gravimetry, and scanning electron microscopy. The TEM photographs revealed a double-layer of CTAB surrounding the NPs and captured the junctions between the NPs and the WLMs. The addition of CTAB-coated AgBr NPs to CTAB/PPA WLMs reduced the flow activation energy by 20% suggesting increased thermal resistance. The added NPs increased the shear viscosity of the WLMs at both 35 and 38 °C, specifically raising the zero-shear viscosity of the WLMs by 85% at these temperatures. The AgBr NP/CTAB/PPA WLMs exhibited a discernible improvement in the relaxation time at 35 °C. The enhanced thermal stability was repeatable after multiple thermal cycles, confirming the reversibility of the microstructures. The junction between the NPs and the WLMs reinforced the micellar structure and contributed to the increased shear viscosity and viscoelasticity of the WLMs.