Surfactant-Modified Cellulose Nanofibril-Stabilized Water-in-Oil Pickering Emulsion Templating for Fabricating Connectivity-Tunable Porous Polymers and Hydrophobic Thermal Insulation Aerogels

Despite the rapid development of cellulose-stabilized oil-in-water emulsions, water-in-oil high internal phase emulsions (HIPEs) remain underexplored, limiting the structural diversity of Pickering-templated porous materials. Here, we introduce TEMPO-oxidized cellulose nanofibrils noncovalently modified with dialkyl-chain cationic surfactants as highly effective stabilizers for water-in-oil HIPEs (>95% internal phase), enabling versatile designs for porous polymers and aerogels. Crucially, adjusting reaction temperature controls pore connectivity in porous polymers, eliminating complex formulation adjustments. Furthermore, this strategy enables the one-pot production of near-superhydrophobic (contact angle ∼147°), thermally insulating (26.7 mW/(m·K)) aerogels with customizable three-dimensional architectures and efficient oil-water separation, without hydrophobic post-treatment. These properties are fine-tuned by modifying the template, and functional additives are easily incorporated to improve flame retardancy and thermal stability. This study presents a novel strategy to tailor porous polymer structures via temperature regulation and pioneers the one-pot fabrication of hydrophobic, thermally insulating cellulose-based aerogels using water-in-oil emulsions.