Solvent-polarity-engineered hyaluronic acid aerogels: Synthesis of transparent nanofiber network for thermal insulation.

Aerogels exhibit superior thermal management properties, while challenges in simple synthesis with mild reaction conditions, optical transparency, and flexibility limit their applications. This study presents a mild approach to produce transparent hyaluronic acid (HA) aerogels without the use of chemical cross-linkers. By regulating solvent polarity through methanol-isopropanol gradient exchange followed by supercritical drying, phase separation is induced, transforming HA molecular chains into a uniform nanofiber network. This structural evolution endows the aerogels with exceptional mechanical strength and flexibility while maintaining high transparency (90 % transmittance and 8.5 % haze at 600 nm). SEM analysis reveals the formation of a nanofiber network with an average diameter of 12.4 nm. Nitrogen adsorption measurements reveals a high surface area of 560.94 m2 g-1. The slender nanofiber network results outstanding thermal insulation, achieving an ultralow thermal conductivity of 0.0243 W m-1 K-1 at a low density of 0.074 g cm-3. This work highlights the critical role of solvent-induced nanofiber assembly in balancing optical and mechanical properties, positioning HA aerogels as sustainable candidates for optically transparent infrared stealth materials.