Review of Hydrogels and Aerogels Containing Nanocellulose

TLDR

Cellulose nanocrystals and nanofibrils are high‑strength, high‑surface‑area nanomaterials whose tunable chemistry and industrial‑scale production make them attractive for polymer composites, yet their hydrophilicity limits use in plastics while enabling reinforced hydrogels and aerogels. This review surveys the rapidly expanding field of nanocellulose‑based hydrogels and aerogels, summarizing over 200 references in tables that cover chemistry, preparation, properties, and applications. The authors discuss physical and chemical cross‑linking, post‑modification, and structural control strategies, highlighting key developments and remaining challenges. Nanocellulose hydrogels and aerogels hold promise across biomedical, energy storage, construction, separations, cosmetic, and food sectors.

Abstract

Naturally derived cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are emerging nanomaterials that display high strength, high surface area, and tunable surface chemistry, allowing for controlled interactions with polymers, nanoparticles, small molecules, and biological materials. Industrial production of nanocelluloses is increasing rapidly with several companies already producing on the tons-per-day scale, intensifying the quest for viable products across many sectors. While the hydrophilicity of the nanocellulose interface has posed a challenge to the use of CNCs and CNFs as reinforcing agents in conventional plastics, it is a significant benefit for creating reinforced or structured hydrogel composites (or, when dried, aerogels) exhibiting both mechanical reinforcement and a host of other desirable properties. In this context, this Review describes the quickly growing field of hydrogels and aerogels incorporating nanocelluloses; over 200 references are summarized in comprehensive tables covering the chemistry, preparation, properties, and applications of "nanocellulose-only" and "nanocellulose-containing" gels. Physical and chemical cross-linking strategies, postmodification steps, and routes to control gel structure are discussed, along with key developments and ongoing challenges in the field. Nanocellulose hydrogels and aerogels show great promise in a wide range of biomedical, energy storage, construction, separations, cosmetic, and food applications.