Four kinds of chitin derivatives, 6-O (2-hydroxyethyl) chitin, 6-O- [2- (2-hydroxyethoxy) ethyl] chitin, 6-O- (2, 3-dihydroxypropyl) chitin and 6-O- (carboxymethyl) chitin, eight kinds of monocarboxylated chitosan derivatives, N- (carboxymethoxyacetyl) chitosan, N- (3-carboxy-propanoyl) chitosan, N- (3-carboxypropanoyl) chitosan, N- (carboxymethyl) chitosan, 6-O- (carboxymethyl) chitosan, N- (carboxymethoxyacetyl) -6-O- (2-hydroxyethyl) chitosan, N- (3-carboxypropanoyl) chitosan and N- (carboxymethyl) -6-O- (2-hydroxyethyl) chitosan, and two kinds of dicarboxylated chitosan derivatives, N- (carboxymethoxyacetyl) -6-O- (carboxy-methyl) chitosan and N- (2-carboxypropanoyl) -6-O- (carboxymethyl) chitosan were prepared and their moisture-absorption and moisture-release properties were examined and compared with those of hyaluronic acid.
The moisture-absorption and moisture release properties of 6-O- (carboxymethyl) chitosan, N- (carboxymethoxyacetyl) -6-O- (carboxymethyl) chitosan and N- (3-carboxypropanoyl) -6-O- (carboxymethyl) chitosan were found quite similar to those of hyaluronic acid. The introduction of carboxyl groups into chitin and chitosan improved their water retention capacity which was also considerably influenced by their positions of substituents and degree of substitution.
