Plant cellulose fibers of width and length ∼0.03 mm and ∼3 mm, respectively, can be completely converted to individual cellulose nanofibers of width and length ∼3 nm and ∼1 µm, respectively, by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation under aqueous conditions and subsequent gentle mechanical disintegration of the oxidized cellulose in water. The obtained TEMPO-oxidized cellulose nanofibers (TOCNs) are new bio-based, crystalline nanomaterials with applications in the high-tech and commodity product industries. Sodium carboxylate groups, which are densely, regularly, and position-selectively present on the crystalline TOCN surfaces, can be efficiently ion-exchanged with other metal and alkylammonium carboxylate groups in water to control the biodegradable/stable and hydrophilic/hydrophobic properties of the TOCNs. TOCNs are therefore promising nanomaterials that can be prepared from the abundant wood biomass resources present in Japan. Increased production and use of TOCNs would stimulate a new material stream from forestry to industries, helping to establish a sustainable society based on wood biomass resources.
Keywords: TEMPO-mediated oxidation; bio-based nanomaterials; cellulose microfibril; cellulose nanofiber; surface modification; sustainable society.