Influence of TEMPO on preparation of softwood nanofibrils and their hydrogel network properties

From an economic and environmental perspective, the use of less chemicals in the production of cellulose nanofibrils (CNFs) is advantageous. In this study, we investigated the oxidation (TEMPO/NaClO₂/NaClO, pH 6.8) of softwood (SW) particles with varying amounts of TEMPO (16, 8 or 0 mg g^-1 of wood). Following, TEMPO-oxidized SW nanofibrils (TO-SWNFs) were obtained by nanofibrillation and their size, morphology, and crystallite size were assessed. Hydrogel networks of TO-SWNFs were prepared and mechanical properties were measured in dH₂O and phosphate buffered saline (PBS) to compare their performance for possible biomedical applications such as wound dressings. The results reveal that the presence of TEMPO is of importance for TO-SWNF network properties, presenting higher eq. H₂O absorption (≈2500 %) and elongation at break (≈10 %) with good wet strength (≈180 kPa). In addition, a decrease in use of TEMPO catalyst from 16 to 8 mg g^-1 of wood is possible, without detrimental effects on hydrogel network properties (dH₂O absorption ≈ 2000 %, elongation at break ≈ 13 %, wet strength ≈ 190 kPa) related to applications as wound dressings.