Formation and interfacial characteristics of water-in-water pickering emulsion stabilized by nanoparticles with different morphologies

Water-in-water (w-w) emulsions are providing valuable strategies for the development of novel sustainable water-based polymer systems. However, the production of long-term stable w-w emulsions remains a significant challenge. The present study investigated the storage stability and interfacial characteristics of w-w emulsions adsorbed by nanoparticles with different morphologies, including cellulose nanocrystals (CNCs), whey protein isolate fibrils (WPIF) and whey protein isolate nanospheres (WPI-NS). Pickering emulsions were fabricated based on the phase-separated system of pullulan (PUL) and polyethylene glycol (PEG). Results indicated that 0.20 wt% CNCs could significantly reduce the droplet size distribution, thus contributing to the stabilization of homogeneous emulsions for 7-day storage. Compared with WPIF and WPI-NS, CNCs favors orderly adsorption and accumulation at the w-w interface, forming a relatively electrically charged layer with a certain interfacial thickness. According to the interfacial rheological behaviors, the CNC-adsorbed interface exhibited gel-like property as the nanoparticle concentration increased from 0.01 wt% to 0.20 wt%, preventing droplet coalescence. The CNC-stabilized interface also showed an increase in interfacial elasticity, which further improved the storage stability of emulsions. The results highlight the promising potential of CNCs as stabilizers for w-w Pickering emulsions. • PUL/PEG ATPS was constructed as a template for a w-w Pickering emulsion. • CNCs improved the storage stability of the w-w emulsion for at least 7 days. • CNCs formed a strong interfacial layer at the w-w interface to prevent coalescence. • CNC-stabilized interface exhibited gel-like properties to enhance emulsion stability.