Individualization of nano-sized plant cellulose fibrils by direct surface carboxylation using TEMPO catalyst under neutral conditions.
A new catalytic oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) and NaClO is applied to hardwood cellulose in water at 60 °C and pH 6.8 with NaClO(2) used as a primary oxidant. The oxidized celluloses with carboxylate content of approximately 0.8 mmol/g were convertible to highly crystalline and individual fibrils 5 nm in width and at least 2 μm in length by disintegration in water. The oxidized celluloses had no aldehyde groups, and high degrees of polymerization of more than 900. Solid-state (13)C NMR and X-ray analyses revealed that the C6 carboxylate groups formed are selectively present on the crystalline fibril surfaces at high densities. Films prepared from the dispersions were transparent and flexible, and exhibited a high tensile strength of 312 MPa even at a low density of 1.47 g/cm(3).
Saito
Tsuguyuki
T
Department of Biomaterials Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
Hirota
Masayuki
M
Tamura
Naoyuki
N
Kimura
Satoshi
S
Fukuzumi
Hayaka
H
Heux
Laurent
L
Isogai
Akira
A
D002264:Carboxylic Acids / Q000032:analysis*; D002384:Catalysis; D002482:Cellulose / Q000737:chemistry*; D003460:Crystallization; D003497:Cyclic N-Oxides; D049329:Nanostructures; D010084:Oxidation-Reduction; D010944:Plants / Q000737:chemistry; D013718:Tensile Strength
D002264:Carboxylic Acids; D003497:Cyclic N-Oxides; D002482:Cellulose; C003959:TEMPO