Crystal transition from hydrated chitosan and chitosan/monocarboxylic acid complex to anhydrous chitosan investigated by X‐ray diffraction

ABSTRACT We have studied the crystal transition behaviors from hydrated chitosan to anhydrous chitosan by X‐ray diffraction analyses. Hydrated chitosan prepared by deacetylation of crustacean α‐chitin was subjected to the two conversion methods, hydrothermal treatment and high‐humidity treatment via chitosan/monocarboxylic acid complex. The transition by hydrothermal treatment progressed with increasing treatment temperature and time, and the rapid transition occurred above 200 °C. Chitosan/acetic acid complex and chitosan/formic acid complex were prepared by immersing hydrated chitosan in acid solution. The transition from chitosan/acetic acid complex to anhydrous chitosan in high relative humidity condition proceeded with increasing temperature and was complete at 80 °C for 1 h, whereas chitosan/formic acid complex did not convert to anhydrous chitosan under the same conditions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53 , 1065–1069