Low-temperature superelastic, anisotropic, silane-crosslinked sodium alginate aerogel for thermal insulation.

Bio-aerogels have attracted much attention owing to their remarkable properties, but their brittle and poor elasticity has limited their further applications. Here, we propose a strategy of in-situ silanization crosslinking combined with unidirectional freeze casting (SUFC) to prepare superelastic sodium alginate (SA) aerogels. The resulting aerogel was ultra-light (0.048 g/cm), high porosity (96.86 %), and self-extinguishing from fire. Aerogels exhibited anisotropic properties, such as low-temperature elasticity (500 g compression at -70 °C 10-cycle, 99.6 % recovery), exceptional fatigue resistance (100-cycle at 50 % strain), and excellent thermal insulation (0.0696 W·m·K). Thus, the SUFC strategy provides considerable freedom for constructing multi-material, lamellar/honeycomb structured alginate-based aerogels, which pave the way to thermal insulation development at low temperatures.