Effect of Ethylenediamine Treatment on Cellulose Nanofibers and the Formation of High-strength Hydrogels

The effect of ethylenediamine (EDA) treatment on cellulose nanofibers (CNFs) remains unclear. To study the effect of EDA treatment on the gelation of the fibrillated CNFs, hydrogels that received 1, 2, and 3 EDA-treatment/washing cycles were prepared and analyzed. Different concentrations of the EDA treatment were also used to prepare hydrogels. Both X-ray diffraction and Fourier transform infrared studies showed that cellulose I/II hybrid hydrogels were fabricated from CNFs via 2 or 3 cycles of 99 wt% EDA treatment and then were washed with water. Field emission scanning electron microscopy observations indicated that the obtained CNF-based hydrogels presented some aggregations via the coalescence of adjacent individual CNFs. Moreover, the hydrogel film with a cellulose I/II crystal structure showed a higher tensile strength of 2.4 MPa and a fracture strain of 23.5%. This was because it had an entangled continuous nanonetwork structure formed after repeated EDA treatment. The authors hope that this work can further stimulate interest in the development of CNF-based hydrogels with multiple structures, properties, and functions for a variety of applications.