Reinforcement with cellulose nanocrystals of poly(vinyl alcohol) hydrogels prepared by cyclic freezing and thawing

Cellulose nanocrystals (CNCs) were incorporated into polyvinyl alcohol (PVA) hydrogels prepared by repeated freeze–thaw processing. The CNC-loaded hydrogels had improved structural stabilities and distinct microstructures, characterized by ordered domains of CNCs. The water sorption of the gels increased with CNC content due to the hydrophilic nature of the cellulose and the decrease in PVA crystallinity. A reinforcement effect was observed in the CNC-loaded samples upon the application of uniaxial, confined compression, with the elastic moduli of the PVA–CNC samples increased relative to pure PVA hydrogels. Hydraulic permeability values were derived from the stress transients: at strains of ∼15 to 20% and greater, the permeability of all samples approached a plateau value reflective of the hindered flow in soft gels which have been compressed, densified and dehydrated.