Solid Templating of Multifunctional Hybrid Nanofiber Aerogels: Bringing a Third Dimension to 2-D Electrospun Nanofibers

Introduced to the scientific community a few decades ago, aerogels have found applications in various fields. However, the brittle nature of inorganic aerogels and low thermal stability in their organic analogs taken together with the complicated processing steps are major challenges to applying the technology at large scale. We present a facile and sustainable solid templating approach to fabricate highly porous and flexible aerogels of hybrid nanofibers of cellulose acetate (CDA) and silica which are produced via sol-gel electrospinning. These ultra-light aerogels exhibit a self-supportive and mechanically robust, three-dimensional network consisting of large secondary pores surrounded by primary pores. SEM micrographs demonstrate a hierarchical architecture consisting of large secondary pores (30-50 mm) interconnected by a network of entangled nanofibers with 2-5 mm primary pores. XPS and in-situ FTIR studies provide evidence that thermal treatment of as-prepared aerogels results in crosslinking the silica-CDA network, therefore, enhancing their mechanical stability and hydrophobicity without compromising their low bulk density (~10 mg.cm^-3) and porosity (>98%). The hybrid aerogels display prolonged superhydrophobicity, high affinity for oil, enhanced thermal stability and flame retardancy. These functional features together with ease of processing make these aerogels interesting candidates for diverse applications ranging from thermal insulation to oil-water sorption.