Research progress of TEMPO oxidation modified natural polysaccharide nanofiber reinforced composites and their functionality

Cellulose and chitin are polysaccharides that abundantly exist in nature and have similar structures. Cellulose and chitin nanofibers prepared by using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidization, not only have good hydrophilicity, biodegradability, biocompatibility and the active chemical properties brought by various functional groups (hydroxyl, carboxyl, acetyl, amino, etc.), but also have the characteristics of large specific surface area, chiral liquid crystal phase, high crystallinity, high transparency and specific nano effect caused by nano size. These natural polysaccharide nanofibers have become one of the research focuses in the field of biomass nanomaterials. In this review, the TEMPO oxidation methods used for the preparation of natural polysaccharide nanofibers, as well as the nanofiber extraction mechanism, were comprehensive summarized. At the same time, the up to now research progress on the as-prepared polysaccharide nanofibers-based composites, such as film, gel, conductive, medical, electromagnetic shielding and environmental materials, with focusing on its mechanical enhancement and function upgradation performance were reviewed. Specific focus is giving to the contributions of the functional groups and nano size of cellulose and chitin nanofibers on the performance improvements of the composites. Finally, the development direction of natural polysaccharide nanofibers and the opportunities and challenges of their applications in various fields are prospected.