Fabrication of cationic chitin nanofiber/alginate composite materials

•Cationic chitin nanofibers were prepared according to the previous method.•Ion exchange of nanofibers with sodium alginate in water gave composite sheets.•The produced sheets were characterized by SEM and XRD measurements.•Alginate was separated from the sheet and characterized.•Ionic cross-linking was probably formed to obtain manipulatable sheets.

We have already found that an amidinated chitin, which was prepared by the reaction of a partially deacetylated chitin with N,N-dimethylacetamide dimethyl acetal, was converted into an amidinium chitin bicarbonate with nanofiber morphology by CO2 gas bubbling and ultrasonic treatments in water. In this study, we performed the fabrication of composite materials of such cationic chitin nanofibers with an anionic polysaccharide, sodium alginate, by ion exchange. When the amidinium chitin bicarbonate nanofiber aqueous dispersion was added to an aqueous solution of sodium alginate, the composite material was agglomerated, which was isolated by centrifugation, filtration, and lyophilization, to form a manipulatable sheet. The morphology of the resulting sheet at nano-scale was evaluated by SEM measurement.