Cellulose nanofibrils prepared from softwood cellulose by TEMPO/NaClO/NaClO2 systems in water at pH 4.8 or 6.8

Catalytic oxidation of softwood cellulose using NaClO and either 2,2,6,6-tetramethylpiperidine-1-oxyl (4-H-TEMPO) or 4-acetamido-TEMPO (4-AcNH-TEMPO) was applied with NaClO2 used as a primary oxidant in an aqueous buffer at pH 4.8 or 6.8. When the 4-AcNH-TEMPO-mediated oxidation was applied to softwood cellulose in water at pH 4.8 and 40 °C, the carboxylate content rose to ∼1.3 mmol/g after reaction for 48 h and the DPv value was more than 1100. This 4-AcNH-TEMPO-oxidized softwood cellulose was mostly converted to individual nanofibrils by mechanical disintegration in water, with uniform widths of 3-4 nm and lengths greater than 1 μm.