Interfacial Engineered Cellulose-Based HIPPEs for Thermal Energy Storage and 3D Printing

The stabilization of phase change materials (PCMs) in high internal phase emulsions (HIPEs) remains particularly challenging due to their inherent properties, significantly hindering their application in functional materials. Here, we introduce a versatile strategy in which oppositely charged cellulose nanofibrils (CNF) and didodecyl dimethylammonium bromide (DDAB) cooperate to construct PCM-in-water high internal phase Pickering emulsions (HIPPEs). The stabilization mechanism relies on a dual barrier: (i) electrostatic adsorption of CNF/DDAB complexes at the oil–water interface forms a dense and reversible interfacial film; (ii) a percolating CNF network in the continuous phase suppresses droplet migration through steric hindrance and viscoelasticity. Consequently, the emulsions remain stable over 30 days at room temperature, these HIPPEs suit diverse oils (including difficult-to-stabilize liquid paraffin) with up to 92% internal-phase volume, serving as green templates/3D printing inks and expanding the fabrication window for programmable HIPPEs in latent-heat storage and thermal management.