Viscoelastic gel formation in nanoclay-based Pickering emulsions with adsorbing non-ionic polymers

The stabilization of Pickering emulsions by nanoclays and water-soluble polymers presents a promising strategy for altering emulsion structure and rheology. In this study, the influence of poly(ethylene oxide) (PEO) with a molecular weight of approximately 100 kg mol⁻¹ on the rheology of oil-in-water emulsions stabilized by the model synthetic nanoclay laponite® was systematically investigated. The addition of PEO, which is known to adsorb onto laponite® particle surfaces, resulted in significant modifications to the microstructure and rheological properties of the emulsions. Flow curves and oscillatory sweeps were analyzed over a specific period to investigate the viscoelastic properties of the Pickering emulsions. The results reveal that PEO at concentrations ≳ 1 wt% significantly enhances yield stress and viscosity. The flow curves were well-fit by the Herschel-Bulkley model, indicating that the emulsions behaved as a soft viscoelastic solid. We expect this is due to the formation of a polymer network within the continuous phase. As the polymer concentration increases, the zeta potential of laponite® decreases, suggesting a reduction in the overall surface charge of laponite® particles with polymer adsorption, which may alter particle interactions and emulsion stability. This charge screening effect results in a strong relationship between the polymer concentration and the properties of the emulsion. Microscopic analysis revealed a decrease in average droplet size, suggesting that PEO contributes to improved interfacial stability. These findings highlight the complex interactions between polymers and clay platelets in determining emulsion performance and provide insights into the applications in soft matter, pharmaceutical formulations, and advanced materials.