TEMPO-oxidized cellulose nanofibers.
Native wood celluloses can be converted to individual nanofibers 3-4 nm wide that are at least several microns in length, i.e. with aspect ratios>100, by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and successive mild disintegration in water. Preparation methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) are reviewed in this paper. Significant amounts of C6 carboxylate groups are selectively formed on each cellulose microfibril surface by TEMPO-mediated oxidation without any changes to the original crystallinity (∼74%) or crystal width of wood celluloses. Electrostatic repulsion and/or osmotic effects working between anionically-charged cellulose microfibrils, the ζ-potentials of which are approximately -75 mV in water, cause the formation of completely individualized TOCN dispersed in water by gentle mechanical disintegration treatment of TEMPO-oxidized wood cellulose fibers. Self-standing TOCN films are transparent and flexible, with high tensile strengths of 200-300 MPa and elastic moduli of 6-7 GPa. Moreover, TOCN-coated poly(lactic acid) films have extremely low oxygen permeability. The new cellulose-based nanofibers formed by size reduction process of native cellulose fibers by TEMPO-mediated oxidation have potential application as environmentally friendly and new bio-based nanomaterials in high-tech fields.
Isogai
Akira
A
Department of Biomaterial Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan. aisogai@mail.ecc.u-tokyo.ac.jp
Saito
Tsuguyuki
T
Fukuzumi
Hayaka
H
D002483:Cellulose, Oxidized / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004548:Elasticity; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure; D055672:Static Electricity; D013718:Tensile Strength; D014867:Water / Q000737:chemistry
D002483:Cellulose, Oxidized; D003497:Cyclic N-Oxides; D014867:Water; C003959:TEMPO