Never
dried bleached hardwood (birch) pulp (UPM Pietarsaari mill, Finland)
was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, Sigma-Aldrich)
at pH 10, then washed with deionized water, and kept at pH 2 for 30
min.58 (link) After washing with deionized water,
the acid form of the carboxylated fibrils were exchanged into their
sodium form by adjusting the pH to 8.5. The TEMPO-oxidized fibrils
were further microfluidized (Microfluidics Corp.) at high-pressure
(2000 bar) through two chambers (200 and 100 μm) arranged in
series. The carboxylic group content of the obtained TOCNF hydrogel
(1.6 wt % dry content) was measured to be 0.6 mmol g–1.
dried bleached hardwood (birch) pulp (UPM Pietarsaari mill, Finland)
was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, Sigma-Aldrich)
at pH 10, then washed with deionized water, and kept at pH 2 for 30
min.58 (link) After washing with deionized water,
the acid form of the carboxylated fibrils were exchanged into their
sodium form by adjusting the pH to 8.5. The TEMPO-oxidized fibrils
were further microfluidized (Microfluidics Corp.) at high-pressure
(2000 bar) through two chambers (200 and 100 μm) arranged in
series. The carboxylic group content of the obtained TOCNF hydrogel
(1.6 wt % dry content) was measured to be 0.6 mmol g–1.
