Poly (acrylic acid-co-acrylamide)/cellulose nanofibrils nanocomposite hydrogels: effects of CNFs content on the hydrogel properties

Nanocomposite hydrogels based on cellulose nanofibrils (CNFs) and poly(acrylic acid-co-acrylamide) were synthesized via in situ free radical polymerization in an aqueous suspension of CNFs. Effects of the inclusion of CNFs with content up to 10 wt% on the swelling properties at different pH and on the compression strength were investigated. The presence of CNFs was shown to strongly reinforce the hydrogel without deteriorating its elasticity. Nanocomposite hydrogel with a content of 10 % CNF supported respectively a strength and deformation about 13 and 2 times higher than that of the neat hydrogel. This effect was explained by the grafting of polymers on the CNFs surface, contributing to an increase in the effective crosslinking density, and improving the interfacial adhesion between polymer chains and CNFs. Moreover, the addition of CNF enhanced the water holding capacity of the hydrogel and caused the system to release urea simulating a fertilizer in a more controlled manner than that with neat hydrogel.