Aqueous condition-tolerated high internal phase oil-in-water Pickering emulsion as building block for engineering 3D functional materials

Conventional high internal phase oil-in-water Pickering emulsions (HIPPEs) have limited applicability as building blocks for fabricating functional materials due to the aqueous condition-dependent stability. The hydrocarbon chain-grafted cellulose nanocrystals (H-CNCs) act as effective stabilizers to stabilize HIPPE. With the attractive hydrophobic forces between the hydrocarbon chains grafted on H-CNC surfaces, the emulsion droplets of H-CNC-stabilized HIPPE exhibit severe flocculation and such HIPPE at stabilizer contents as low as 0.06 w/v% (based on emulsion volume) display promising rheologies such as shear-thinning behaviors, viscoelasticity, rapid thixotropic recovery, and satisfactory stability against inter-droplet repulsions under a wide range of different aqueous conditions (pH scale: 3 to 12, ionic strength: 0 to 1 M NaCl and stabilizer content: ≥ 0.06 w/v%) and oil volume fractions (66% − 83%). By varying aqueous conditions/compositions and oil volume fractions while maintaining robust stability and promising rheological behaviors, the HIPPEs show the broad applicability as building blocks to print or build functional three-dimensional materials such as ultra-lightweight porous scaffolds with tunable pore sizes, stimuli-responsive hydrogels for controlled release of internal phase, elastic hydrogel sensors susceptible to weak forces and porous material with excellent thermal insulation performance, demonstrating the versatility of such H-CNC-stabilized HIPPEs in engineering state-of-the-art functional materials.