A. Yamamoto et al., CONFORMATIONAL BEHAVIOR OF CHITOSAN IN THE ACETATE SALT - AN X-RAY STUDY, Bioscience, biotechnology, and biochemistry, 61(7), 1997, pp. 1230-1232
A well-defined X-ray fiber pattern of chitosan acetate was obtained by
immersing a tendon chitosan, prepared from a crab tendon chitin by a
solid-state N-deacetylation, in an aqueous acetic acid-isopropanol sol
ution at 110 degrees C, This pattern was very similar to that of chito
san salts with some inorganic acids, such as HF, HCl, and H2SO4, in wh
ich chitosan chains form an 8/5 helix, indicating that chitosan acetat
e also take ap this conformation, This information may give an influen
tial clue to the chitosan conformation in the aqueous acetic acid solu
tion, the most popular solvent for chitosan. However, after one month
of storage of the chitosan acetate, the fiber pattern, the density and
its IR spectrum changed to those of the anhydrous polymorph of chitos
an, suggesting that the acetic acid was removed accompanied with water
molecules from the crystal during storage and that the polymorph can
be obtained not only by annealing chitosan, brat also through the chit
osan acetate.