Sclerotization-Inspired Aminoquinone Cross-Linking of Thermally Insulating and Moisture-Resilient Biobased Foams

Thermally insulating foams and aerogels based on cellulose nanofibrils (CNFs) are promising alternatives to fossil-based thermal insulation materials. We demonstrate a scalable route for moisture-resilient lightweight foams that relies on sclerotization-inspired Michael-type cross-linking of amine-modified CNFs by oxidized tannic acid. The solvent-exchanged, ice-templated, and quinone-tanned cross-linked anisotropic structures were mechanically stable and could withstand evaporative drying with minimal structural change. The low-density (7.7 kg m -3 ) cross-linked anisotropic foams were moisture-resilient and displayed a compressive modulus of 90 kPa at 98% relative humidity (RH) and thermal conductivity values close to that of air between 20 and 80% RH at room temperature. Sclerotization-inspired cross-linking of biobased foams offers an energy-efficient and scalable route to produce sustainable and moisture-resilient lightweight materials.