Preparation of Self-supporting Bagasse Cellulose Nanofibrils Hydrogels Induced by Zinc Ions

Cellulose hydrogels are often prepared from native cellulose through a direct cellulose dissolution approach that often involves tedious process and solvent recovery problems. A self-supporting cellulose hydrogel was prepared by gelation of the TEMPO-oxidized bagasse cellulose nanofibrils (CNF) triggered by strong crosslinking between carboxylate groups and Zn2+. TEMPO process was used to generate negatively charged carboxylate groups on CNF surface to provide a high binding capability to Zn2+. Three TEMPO-oxidized CNFs of different carboxylate contents were prepared and characterized. TEM and AFM microscopes suggested that the sizes of CNFs were fined down and carboxylated cellulose nanofibrils (TOCNFs) of 5-10 nm wide, 200-500 nm long, and carboxylate contents 0.73-1.29 mmol/g were obtained. The final structures and compressive strength of hydrogels were primarily influenced by interfibril Zn2+-carboxylate interactions, following the order of TOCNFs concentration > content of carboxylate groups > concentration of zinc ions. A CO2 sensitive self-supporting cellulose hydrogel was developed as a colorimetric indicator of food spoilage for intelligent food packaging applications.