Nanocelluloses as new generation materials: natural resources, structure-related properties, engineering nanostructures, and technical challenges

Valorization of cellulosic biomass by processing it into functional nanoscale building blocks enables more sustainable use of resources and an expansion of its potential applications. Nanocelluloses are attractive engineered bionanomaterials with different morphologies, interesting properties, and surface functionalities that depend on the choice of specific resources, synthesis protocols, and processing conditions. This review highlights different natural resources (i.e., plants, bacteria, algae, animals) of nanocelluloses, production methods (i.e., mechanical, physical, chemical, mechanochemical, physicochemical, biological), and their morphologies (i.e., nanoparticles, nanocrystals, nanofibers). The structure-related properties of nanocelluloses (i.e., crystalline structures, mechanical strength, interactions with water, rheological properties, biocompatibility, nontoxicity, and biodegradation) are covered in particular detail. Surface modification by functional groups, macromolecules, and nanoparticle deposition are emphasized to improve their processability and compatibility. The assembly of nanocelluloses into engineered structures (hydrogels, aerogels, macroscopic filaments, and membranes) can produce materials with novel functionalities for various technological applications. Finally, the current state of research, future prospects, and challenges for the commercialization of nanocelluloses are addressed.