High Humidity Shaker Aging to Access Chitin and Cellulose Nanocrystals

Nature’s potential in affording functional biomaterials is often hindered by extraction conditions. To isolate nanocrystalline domains in polysaccharides high solvent usage is warranted while low reactivity and yields are also limiting factors. In this report, the first solvent-free pathway to access carboxylated chitin and cellulose nanocrystals with excellent mass balance is described, relying on a new method coined high-humidity shaker aging (HHSA). The method involves a brief and mild grinding of the polysaccharide with ammonium persulfate followed by an aging phase under high-humidity and on a shaker plate. Insights into the mechanism were uncovered, which highlighted the unique role of high humidity to afford a gradual uptake of water by the material up to deliquescence when the reaction is complete. This process was then validated for direct synthesis of nanocrystals from biomass sources including crab and soft wood pulp.