Aerogels are materials with ultra-low density and ultra-high porosity that could be even more unique in their renewability and biodegradability when derived from natural polymer precursors. Highly crystalline nanocellulose are particular attractive precursors due to their intrinsic high strength and ability to hydrogen bond into resilient structures. This paper presents a diverse range of aerogels assembled from ultrathin and long cellulose nanofibrils (CNFs) (1-2 nm wide and 500-1000 aspect ratio) derived from TEMPO-mediated oxidation aided with mechanical defibrillation. CNFs can be facilely assembled from dilute aqueous suspensions by ice-templating into hydrogels and then freeze-dried into aerogels in varied densities (1.7-18.7 mg/cm<sup>3</sup>), porosities (98.8-99.9 %), specific surfaces (13-200 m<sup>2</sup>/g) and exhibit unique amphiphilicity, super absorption capacity toward both polar (up to 210 g water/g aerogel) and non-polar liquid (up to 375 g chloroform/g aerogel) as well as excellent wet resiliency in aqueous environment. This amphiphilicity could facilitate chemical modification in organic media, as demonstrated by one-step crosslinking and hydrophobization using methylene diphenyl diisocyanate (MDI) via reacting CNF surface hydroxyls with the isocyanate groups, resulting in a further improvement in thermal stability, specific surface, mechanical properties and hydrophobicity, as well as achieving a scaling law effect between the mechanical properties and density. In this presentation, assembling CNFs alone and in the presence of functional chemicals into a range of wet resilient aerogels will be detailed and the versatility of the assembled aerogels in water-oil or water-hydrocarbon separation as well as other potential application will be demonstrated.

Amphiphilic and resilient cellulose nanofibril aerogel: Assembling, structural and properties analyses

251st National Meeting (2016)

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