High-Internal-Phase Pickering Emulsions Stabilized by Polymeric Dialdehyde Cellulose-Based Nanoparticles

Developing green and sustainable micro/nanoparticles that can be used to stabilize high-internal-phase Pickering emulsions (HIPPEs) via simple methods is of great significance. Herein, polymeric nanoparticles, fabricated via a facile one-step interfacial Schiff base reaction between dialdehyde cellulose (DAC) and aniline, were successfully used to stabilize oil-in-water HIPPEs. The ratio between aldehyde groups in DAC and aniline demonstrated a great effect on the emulsifying performance of the resultant dialdehyde cellulose-aniline nanoparticles (DANPs). DANPs prepared with suitable high ratios of aldehyde groups to aniline (from 20:1 to 6:1) were able to stabilize oil-in-water HIPPEs with various oil types, such as toluene, hexadecane, styrene, and even viscous edible sunflower oil. In comparison, DANPs fabricated with the ratios of aldehyde groups in DAC to aniline of 4:1 and lower were unable to stabilize HIPPEs. In addition, HIPPEs stabilized by DANPs prepared with higher ratios of aldehyde groups to aniline have smaller droplets, higher storage modulus, and better thermal stability. In particular, DANP-stabilized HIPPEs had good stability at diverse environmental conditions, e.g., higher temperatures (of up to 80 °C) and higher electrolyte concentrations (of at least 50 mM NaCl). Although phase separation occurred to all DANP-stabilized HIPPEs after a freeze–thaw treatment, gel-like HIPPEs could be easily refabricated by handshaking, for at least five cycles of the freeze–thaw treatment. In addition, macroporous poly(melamine-formaldehyde) (PMF) foams were prepared using DANP-stabilized HIPPEs as a template. Therefore, this study further advances the design of stable HIPPEs using polysaccharide-based nanoparticles and the potential of HIPPEs in practical applications.