Amphiphilic Nanofiber-Based Aerogels for Selective Liquid Absorption from Electrospun Biopolymers

Hierarchically structured and ultralight pullulan/poly(vinyl alcohol) (pullulan/PVA) aerogels or sponges are prepared from short electrospun nanofibers using solid templating. The architecture of the aerogel consists of cell-like pores of 50-100 mu m interconnected by a network of entangled nanofibers with 2-5 mu m pores. Such structures allow rapid liquid uptake with high liquid holding capacities at the same time. The amphiphilic nature of the aerogel from the electrospun biopolymer is switched by chemical vapor deposition of silane. This allows the selective separation of liquids based on their different relative dielectric constants, which is of high interest for oil spilled waters and produced water. Furthermore, silylation improves the aerogel's overall mechanical stability by 18% while increasing its density by only 5%. Scanning electron microscopy in situ compression studies reveal the importance of the fibrous entanglement and the open-porous architecture for the high bendability and mechanical resilience of the aerogels. Solid templating of short electrospun nanofibers facilitates the design of a fascinating class of ultralight aerogels while prevailing the fibrous character and the versatility of electrospinning.