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

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Journal Title
Journal ISSN
Volume Title
A2 Katsausartikkeli tieteellisessä aikakauslehdessä
Date
2018-11-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
27
122-148
Series
Progress in Polymer Science, Volume 86
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.
Description
Keywords
Catalytic oxidation, Cellulose, N-oxyl radical, Nanofibril, Position-selective reaction, Surface modification, TEMPO
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Citation
Isogai, A, Hänninen, T, Fujisawa, S & Saito, T 2018, ' Review: Catalytic oxidation of cellulose with nitroxyl radicals under aqueous conditions ', Progress in Polymer Science, vol. 86, pp. 122-148 . https://doi.org/10.1016/j.progpolymsci.2018.07.007