Fabrication of elastic composite hydrogels using surface-modified cellulose nanofiber as a multifunctional crosslinker

We fabricate composite hydrogels using surface-modified cellulose nanofiber (CNF) and N-isopropylacrylamide (NIPAm) as a multifunctional crosslinker and monomer, respectively. We expect to produce unique network structures that lead to elastomeric properties rarely reported for CNF-based materials. The modification of CNF is performed to introduce polymerizable vinyl groups onto the surface of CNF via condensation between the surface hydroxyl groups and 3-(trimethoxysilyl)propylmethacrylate. The modification and morphology of the surface-modified CNF (mCNF) are confirmed by FTIR, solid-state NMR, and FE-SEM, respectively. We conduct in situ radical polymerization under various conditions using mixtures of the mCNF aqueous suspension, NIPAm monomer, radical initiator, and catalyst. The mechanical properties of the obtained hydrogels (water content = 90 wt %) are evaluated. The gels can be elastically stretched to more than 700 times their original lengths and exhibit an apparent shape recovery with a small permanent deformation (similar to 1/5 of the applied deformation under the gravity field). (C) 2015 Wiley Periodicals, Inc.