Formation of high strength double-network gels from cellulose nanofiber/polyacrylamide via NaOH gelation treatment

Previously, we reported an efficient method to prepare tough hydrogels from cellulose nanofibers using an alkali treatment which had an nano-network structure. In this study, polyacrylamide/cellulose nanofiber (PAM/CNF) double-network (DN) gels were synthesized by simply using 15 wt% NaOH at room temperature. The compression properties and morphology of the gels were investigated. The main findings showed that the compressive stress of the PAM/CNF DN gel (CNF content of 5.7 wt%) was more than 15-fold higher than the pure PAM. When compared with the PAM/CNF gel prepared without alkali treatment, the mechanical properties of the PAM/CNF DN gel showed approximately 2-fold improvement. Analysis of this DN gel morphology further demonstrated that the CNF network (formed via 15 wt% NaOH treatment) was embedded in the PAM matrix, thereby increasing the strength of the hybrid gels. In summary, PAM/CNF DN gels with significantly improved mechanical properties could be prepared using a simple method, which provide great potential as bio-medical load-bearing gel materials.