Hairy Cellulose Nanocrystals: From Synthesis to Advanced Applications in the Water–Energy–Health–Food Nexus Free

Cellulose and its derivatives are well recognized for their biodegradability, biorenewability, and abundance. Nanocelluloses have been one of the focuses of sustainable nanotechnology for applications spanning from mechanical reinforcement and rheology modification to catalysis, separation, energy storage, wearable devices, food additives, and biomedicine. Hairy cellulose nanocrystals (HCNCs) are a newly emerged class of nanocelluloses that are made up of a crystalline body, similar to the conventional cellulose nanocrystals (CNCs), sandwiched between two layers of highly functionalized disordered cellulose chains (“hairs”). HCNCs are directly synthesized from cellulose fibrils via acid-free controlled oxidation reactions. The hairs impart unique capabilities to HCNCs that are otherwise difficult or often impossible to achieve with conventional nanocelluloses, such as CNCs and cellulose nanofibrils (CNFs). HCNCs, bearing more than one order of magnitude higher density of functional groups on their hairs compared with CNCs, benefit from strong electrosteric or steric stability and may undergo amorphous region (hairs)-mediated self-assembly. This chapter provides a comprehensive overview of HCNC synthesis and soft matter platforms, such as films, hydrogels, aerogels, and nanocomposites for a plethora of applications in the water–energy–health–food nexus.