Superhydrophobicity of nanofibrillated cellulose materials through polysiloxane nanofilaments

The wetting behavior of nanofibrillated cellulose (NFC) was drastically changed from hydrophilic to superhydrophobic, achieving limited contact angle hysteresis. Remarkably, superhydrophobicity was attained for a variety of morphologies, namely dense and porous films, foams and powders, thus exploiting a wide spectrum of cellulose manifestations. The superhydrophobic behavior resulted from the combined action of hydrophobic polysiloxane nanofilaments, formed by controlled reaction of methyltrichlorosilane with water at the surface of NFC fibrils, and the NFC substrates surface morphology, established by various drying methods of the nanofibrils. In particular, the optimal conditions for polysiloxane nanofilaments growth, with identification of various regimes of coating versus nanofilaments growth, were identified. Depending on the morphology, we demonstrated that modified NFC materials can act multiple roles, such as superhydrophobic liquid-infused lubricating surfaces, filters for dodecane drops capture from a nebulized dodecane/water mixture, hydrocarbon absorption from an aqueous phase, with absorbance capacity as high as 50 g dodecane /g foam , and beds to separate hydrocarbon/water mixture. As such, the versatile combination of two materials with nanoscale features (nanocellulose and nanofilaments), which provide multi-tier topography and unprecedented wetting characteristics, can serve for all those applications, in which liquid mixture behavior (e.g. water/hydrocarbon) needs to be controlled.