Controlled stiffness and diffusivity of poly(ethylene glycol) hydrogel formed with cellulose-nanofiber framework

Abstract

Hydrogels composed of polymer networks are widely used in industry and scientific research for high water retention and unique mechanical properties. Nevertheless, in ordinary hydrogel formation, the trade-off relationship between stiffness and mesh size remains a crucial consideration for practical applications. This study describes a facile approach to controlling hydrogel stiffness and mesh size by hybridizing poly(ethylene glycol) diacrylate (PEGDA) and methacrylated TEMPO-oxidized cellulose nanofibers (T-CNFMA). After disintegrating T-CNF by ultrasonication, T-CNFMA was synthesized resulting in a degree of substitution of 2.04 mmol/g. Incorporation of T-CNFMA in the PEGDA network allowed for independent control of hydrogel stiffness and mesh size by reinforcing the whole hydrogel network as a framework. Consequently, the swelling ratio and shear modulus could be manipulated by controlling the PEGDA/T-CNFMA ratio. Structural analyses revealed that an increase in the T-CNFMA content in the presence of a low amount of PEGDA resulted in a large mesh size with a constant stiffness. The diffusivity test was also consistent with the properties of the hydrogels. This result indicates that the incorporation of T-CNF in hydrogel network is useful to control the physical property of the hydrogel, especially for varying mesh size, regardless of stiffness alteration.