Efficient green approaches for the preparation of physically crosslinked chitin gel materials by freeze-induced self-assembly.

Chitin derived from crustacean biomass has great potential for the production of eco-friendly materials. However, one challenge is its insolubility in regular solvents. Herein, the gelation of chitin alkali suspension was induced via freeze-thawing approach. The as-prepared hydrogels with/without dialysis treatment were freeze-dried into solid foams to display "dry durian fruit" appearance. It was found that dialysis did influence the properties, in which the dialyzed samples exhibited superior water content, swelling ratio, porosity, thermal stability, and smoother surface morphological results. Moreover, the dialyzed chitin foams exhibited nearly the same level of thermal stability compared to chitin powder. With respect to formation mechanisms, we propose that alkali treatment swells chitin and the freezing process deconstructed and weakened H-bonding, while the weakened H-bonding residue self-assembly contributed to hydrogel formation. This research represents a simple and green route for converting chitin suspension to gel materials. Unlabelled Image • A simple and green strategy can process insoluble chitin powder into a hydrogel and solid foams. • The as-prepared chitin foams exhibit almost the same level of thermal stability to pure chitin powder. • A possible gel formation mechanism is also proposed. [ABSTRACT FROM AUTHOR]