Ultralight, mechanically robust, thermal-insulated and superhydrophobic electrospinning lignin-based nanofiber aerogels.

Lignin-based nanofibers (LNFs) were fabricated via electrospinning using a mixture of lignin and polyvinyl alcohol (PVA) as the spinning solution. Next, the LNFs were sequentially subjected to homogeneous shearing, freeze-drying, in-situ thermal cross-linking, and thermochemical vapor deposition involving treatment with organosilanes to obtain ultralight, mechanically robust, thermal-insulated, and superhydrophobic LNF aerogels (LNFAs). Careful adjustment of the LNF content aided in precise control and optimization of the network structure, density, and porosity of the obtained LNFAs, which ultimately affected their compressive strength and thermal conductivity (25.46 ± 1.32 to 31.06 ± 0.09 mW⋅m-1⋅K-1). Moreover, the lignin content in LNFs also affected the nanofiber diameters, thereby regulating the compressive strength of LNFAs (3.40 ± 0.17 to 4.91 ± 0.16 kPa). The LNFAs with the lignin/PVA ratio of 2.5 and the LNF content of 0.7 g (LNFAs-2.5) possessed the density of 8.88 ± 0.13 mg⋅cm-3, porosity of 99.31 ± 0.01 %, and compressive strength of 4.91 ± 0.16 kPa under a compression strain of 60 %, and it still maintained good composition structures supported even after 150 compression and rebound cycles. The LNFAs-2.5 possessed favorable properties of high-water resistance with contact angle of 150.4° and low thermal conductivity, making synthetic warmth retention materials superior to down feathers.