High internal phase pickering emulsions stabilized by ODSA-functionalized cyclodextrin metal-organic frameworks for extrusion 3D printing application

Cyclodextrin metal-organic frameworks (CD-MOFs) are novel ordered porous materials with high adsorption and interfacial stabilization. Herein, oil-in-water emulsions stabilized by octadecenylsuccinic anhydride (ODSA) modified CD-MOFs (OCMs) with a volume fraction of 0.8 were prepared. A contact angle of 92° was achieved when 5 wt% ODSA was added to OCMs, which promoted the stabilization of OCMs-emulsions with homogeneous and spherical droplets. Moreover, the emulsion possessed a small droplet size of 7–9 μm (d4,3), long-term storage stability and flocculation resistance. At the pH range of 10–12, the emulsions had a more desirable structure with a gel-like elastic network and a dense particle layer covered onto the droplets, which were verified by SEM and cryo-SEM. The 2D cross-linked particle film at the water-oil interface and the 3D cross-linked gel-like particle network in the continuous phase synergistically improved the stability of coalescence and flocculation of the OCMs-HIPPEs. Afterwards, the OCMs-HIPPEs with no discernible oil were used as printing ink, which had no droplet coalescence in the freeze-thaw and showed high 3D printing quality and shape retention. Overall, this study demonstrates that the ODSA-modified CD-MOFs with favorable properties may be used to fabricate high-quality edible HIPPEs for extrusion 3D printing ink.