Storage of partially deacetylated chitosan films

Chitosan has wide-ranging applications as a biomaterial, but its stability in storage is not widely known. The objective of this study was to evaluate the storage stability of films prepared from chitosan of 77% deacetylation , Both the neutralized and acetate films were evaluated, as chitosan salts offer the advantage of being soluble in water at the neutral-to-basic pH ra nge. Aqueous solutions containing 0.5-5% acetic acid were used as solvents. The X-ray diffraction pattern, the IR spectrum, water uptake, and solubili ty of the films were influenced by the presence of the N-acetyl functionali ty, the acetate ions, and storage of the films. The anhydrous chitosan crys tal in the neutralized films was unstable to storage at 4 degrees C and 28 degrees C, Its formation, as well as that of the hydrated crystal, were fur ther hindered by the presence of even small quantities of the acetate ions. The resultant amorphous nature of the acetate films, coupled with the acid ifying action of the acetic acid, led to greater water uptake and solubilit y compared to the neutralized films, Storage reduced the differences betwee n the neutralized and acetate films. It also minimized the influence of the initial acetic acid content on the IR absorption and water uptake of the a cetate films, exerting its leveling effects mainly within the first meek of storage. Using a lower storage temperature of 4 degrees C or heating the f ilms for 2 h at 120 degrees C prior to storage did not significantly modify the results. A pertinent factor appears to be the degree of deacetylation of the chitosan that was used to prepare the films. (C) 1999 John Wiley & S ons, Inc.