Robust methylcellulose hydrogels reinforced with chitin nanocrystals.

Many reinforcing materials have been investigated to improve the mechanical performance of the host matrices. Among reinforcing materials, α-chitin nanocrystals (α-ChNCs) from shrimp or crab shells were recently used as reinforcing nanofillers of polymer nanocomposites. In this study, novel β-chitin nanocrystals (β-ChNCs) were employed for the reinforcing nanomaterial of methylcellulose (MC) hydrogels. They were obtained from cuttlefish bone by acid hydrolysis. The β-ChNCs had a different morphology with an irregularly granular shape, unlike the rod-like shape of α-ChNCs, and were stable in their aqueous suspensions. Subsequently, the MC nanocomposite hydrogels were prepared by mechanically mixing the water-soluble MC in aqueous β-ChNCs suspension. The formation rate and mechanical strength of MC nanocomposite hydrogels were dramatically increased even at a low content of β-ChNCs. This increment in the gelation rate and gel strength might be associated with the formation of additional physical crosslinking between crystalline β-ChNCs and MC molecular chains, as well as the original hydrophobic interaction between the MC molecules. Therefore, dual physical crosslinking was constructed in the MC nanocomposite hydrogels. These robust MC composite hydrogels offer great potential for various biomedical applications.