Eco-Friendly Pickering Emulsion Stabilized by Silica Nanoparticles Dispersed with High-Molecular-Weight Amphiphilic Alginate Derivatives

O/W Pickering emulsions formed with silica nanoparticles adsorbed with amphiphilic alginate derivatives produced a longer stability. Ugi-Alg was obtained by a mild and efficient Ugi four-component condensation reaction, and its structure of Ugi-Alg was confirmed by 'H nuclear magnetic resonance and Fourier transform infrared spectroscopies. Dynamic light scattering and transmission electron microscopy measurements were then performed to characterize the aggregation behavior of SiO2/Ugi-Alg mixture in aqueous solution. The positioning of the silica particles at the oil water interface was obtained through confocal laser scanning microscopy. The long-term stability and rheological property of Pickering emulsions stabilized by Ugi-Alg and SiO2 nanoparticles were respectively investigated by Turbiscan Lab Expert stability analyzer and rotational rheometer. The rheological behaviors of the emulsions were studied and results showed that UgiAlg with high molecular weight led to more rigid structures. This trend can be justified by the formation of silica particle strong network attributed to the entanglement and bridging of Ugi-Alg. The results indicated that adjusting the amount of silica nanoparticles and Ugi-Alg molecular-weight could be a suitable means for manipulating stability of polymer nanoparticles-based Pickering emulsions. This process would be of great application prospect for the preparation of Pickering emulsions stabilized by sustainable polymer surfactant and nanoparticles.