Surface phthaloylation of chitin nanofiber in aqueous media to improve dispersibility in aromatic solvents and give thermo-responsive and ultraviolet protection properties
Phthaloylation of chitin nanofiber (NF) was achieved by reaction with phthalic anhydride in aqueous media. The phthaloyl group was quantitatively introduced into an amino group of a surface-deacetylated chitin NF surface. The characteristic nanofiber network structure was maintained after phthaloylation. The NFs were dispersed homogeneously in organic solvents, and even in several aromatic solvents, due to the high solvation interactions with the phthaloyl group. In addition, the homogeneous dispersions in aromatic solvents had reversible thermo-responsive properties and exhibited a dispersive-to-precipitate phase transition response at approximately 25 °C. Due to the presence of the phthaloyl group, the NF dispersion and the nano-composite film cut harmful ultraviolet light.