Shell Thickness Dictates Electrolyte Concentration-Mediated Rheology Behavior of Core–Shell Nanoparticles Adsorbed at an Interface

Core-shell nanoparticles exhibit diverse structural forms and excellent interfacial activity, significantly enhancing the rheological properties and mechanical strength of the interfacial film upon adsorption at the air-liquid interface. This study employs a physical adsorption method to prepare polyvinylpyrrolidone (PVP)-coated silica core-shell nanoparticles with varying shell thicknesses, which are designated as CPs8 and CPs40. The research investigates the compression behavior and shear rheological properties of CPs8 and CPs40 interfaces under different electrolyte concentrations. The findings indicate that the interparticle forces in CPs40 are primarily governed by interactions between particle shells. Increased electrolyte concentration has a negligible influence on the interface compression behavior of CPs40, but the shear moduli significantly increase, enhancing resistance to tangential stress. Conversely, the interparticle forces in CPs8 are predominantly core-core attractions. While electrolyte concentration has a limited impact on the shear behavior of CPs8, it markedly influences its compression behavior. As the electrolyte concentration rises, the attractive forces between particles increase, leading to higher degrees of particle agglomeration and forming a stable, irreversible particle network, which better resists interface compression. Furthermore, while the interface shear rheological characteristics of CPs40 are markedly influenced by electrolyte concentration, the CPs8 interface demonstrates a stronger viscoelastic advantage and higher mechanical strength.