Diverse nanocelluloses prepared from TEMPO-oxidized wood cellulose fibers: Nanonetworks, nanofibers, and nanocrystals

• Published in: Current opinion in solid state & materials science Vol. 23; no. 2; pp. 101 - 106
• Main Authors: Isogai, Akira, Zhou, Yaxin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2019
• Subjects: Microfibril; Nanocrystal; Nanofiber; Nanonetwork; TEMPO; Wood cellulose; Wood cellulose; Microfibril; Nanonetwork; Nanofiber; CNC; CNF; TEMPO; Nanocrystal
• ISSN: 1359-0286
• DOI: 10.1016/j.cossms.2019.01.001

[Display omitted] •TEMPO-oxidized wood cellulose fibers can be converted to diverse nanocelluloses.•Cellulose nanonetworks, nanofibers, and nanocrystals dispersed in water are obtained.•Cellulose nanofibers and nanocrystals have homogeneous widths of ∼3 nm.•Cellulose nanocrystals have needle-like morphologies with aspect ratios of ∼50.•Cellulose nanofibers have aspect ratios of > 150. When wood cellulose fibers are oxidized with NaClO and catalytic amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and NaBr in water at pH 10, significant amounts of sodium carboxylate groups (≤1.7 mmol/g) are introduced into the oxidized celluloses. The original fibrous morphologies and cellulose I crystal structures are unchanged by oxidation. The TEMPO-oxidized cellulose fibers can be converted to partially fibrillated nanonetworks, completely individualized cellulose nanofibers with high aspect ratios, and needle-like cellulose nanocrystals with low aspect ratios by controlling the conditions of mechanical disintegration in water. It is therefore possible to prepare diverse nanocelluloses with different morphologies and properties from the same TEMPO-oxidized cellulose fibers, for various end uses and applications. All TEMPO-oxidized nanocelluloses contain large amounts of carboxylate groups. These provide scaffolds for versatile surface modification of nanocelluloses by simple ion exchange of sodium for other metal ions and alkylammonium ions.