Cellulose nanowhisker aerogels

Abstract

Aerogels were prepared through the self-assembly of cellulose nanowhiskers in a benign manner. Preparation of these aerogels only requires sonication in water to form a hydrogel, solvent exchange with ethanol and supercritical CO2 drying. Aerogels were prepared with varying cellulose nanowhisker content and characterised with X-ray diffraction, BET analysis and electron microscopy. Their density and porosity varied linearly with varying concentrations of cellulose nanowhiskers in the initial hydrogel and confirmed that gel shrinkage upon drying was limited to, on average, 6.5%. We achieved densities down to 78 mg cm−3 with high specific surface areas up to 605 m2 g−1. Mesopores displaying a bimodal size distributions with maxima centred around 4.3 and 15.5 nm accounted for 5–11% of total pore volume. Micropores accounted for less than 1% of total pore volume with the remaining fraction being macropores.