تهيه كيتوسان با درجه استيل زدايي متفاوت و مقايسه روش هاي مختلف شناسايي آن

One of the important parameters to determine the propertis of chitosan is the degree of deacetylation (DD) of this natural polymer. In this work, seven grades of chitosans polymer have been synthesized. The effect of time (under constant conditions) on the reaction of deacetylation was evaluated. Results indicated that, there was a direct proportion between the time length of the reaction and DD of polymer. Also, the effects of DD and molecular weight on crystal linity of chitosan powder have been determined. Results indicate that DD has a great effect on crystallinity; it means that initially, the percent of crystallinity is increased with the increase in DD, and then it is decreased. The results of polymer solution viscosity to specify chitosansʹ molecular weight confirm that, variation in inherent viscosity is probably related to hydrogen bonding in polymer molecular structure and errors which might have occurrec due to employment of this method. In addition, two different methods have been used to characterize the degree of deacetylation including; infrared spectroscopy and hydrogen bromide titration. Results have indicated that DD values totally depend on a specific analytical method employed. In all samples, DD found by titration method are greater than results obtained by infrared spectroscopy. Therefore, the methods of DD values determination must always be known and specified.