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Cellulose nanocrystals (CNCs) are entering the marketplace as new high-strength nanoadditives from renewable resources. These high aspect ratio particles have potential applications as rheological modifiers, reinforcing agents in composites, coatings, and porous materials. In this work, chemically cross-linked CNC aerogels were prepared based on hydrazone cross-linking of hydrazide and aldehyde-functionalized CNCs. The resulting aerogels were ultralightweight (5.6 mg/cm 3 ) and highly porous (99.6%) with a bimodal pore distribution (mesopores 1 μm). Chemically cross-linked CNC aerogels showed enhanced mechanical properties and shape recovery ability, particularly in water, compared to previous reports of physically cross-linked CNC aerogels. Specifically, the aerogel shape recovered more than 85% after 80% compression, even after 20 compress and release cycles. These CNC aerogels can absorb significant amounts of both water (160 ± 10 g/g of aerogel) and dodecane (72 ± 5 g/g of aerogel) with cyclic absorption capacity. We demonstrate that CNC aerogels can be used as superabsorbents and for oil/water separations and they may also find application as insulating or shock-absorbing materials. The cross-linking technology developed here presents new ways to design CNC networked structures and suggests an alternate route to incorporate CNCs into matrix materials, such as epoxies and foams.
Yang et al. (Wed,) studied this question.