Review: Catalytic oxidation of cellulose with nitroxyl radicals under aqueous conditions

By A. Isogai, T. Hänninen, Shuji Fujisawa, Tsuguyuki Saito. Progress in polymer science, 2018

280 citations recorded by the source corpus.

Abstract 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation is a unique reaction to native and regenerated celluloses, and has advantages in terms of position-selective reaction at room temperature under aqueous conditions. When the TEMPO/NaBr/NaClO oxidation is applied to native celluloses in water at pH 10 under suitable conditions, the C6-primary hydroxy groups present on crystalline cellulose microfibril surfaces are mostly converted to sodium C6-carboxylate groups. Anionic sodium glucuronosyl units are densely, regularly, and position-selectively formed on crystalline cellulose microfibril surfaces, while maintaining the original cellulose morphology, cellulose I crystal structure, crystallinity, and crystal width. When TEMPO-oxidized celluloses (TOCs) prepared from, for example, wood cellulose have sodium C6-carboxylate contents >1 mmol/g, transparent highly viscous gels consisting of TEMPO-oxidized cellulose nanofibrils (TOCNs) with homogeneous widths of ≈3 nm and lengths >0.5 μm, dispersed at the individual nanofiber level, are obtained by gentle mechanical disintegration of TOCs in water. Alternative systems are as follows: TEMPO/NaClO/NaClO2 system, TEMPO electro-mediated oxidation, etc. TOCNs are promising new plant-based renewable nanofibers applicable to high-tech material fields.

Subfields: Biomaterials, Biomedical Engineering, Plant Science

View Paper: https://www.semanticscholar.org/paper/463dcf830cc4edd3ff1698838ab58e762a2efde9