Hydrogel membranes based on gum tragacanth with tunable structures and properties. II. Comprehensive characterization of the swelling behavior

Hydrogel membranes based on gum tragacanth (GT), with a wide range of crosslinking densities (0.8323.87 X 10-6 mol/cm3) and swelling capacities (1201580 g/g), were prepared with the aid of heat alone and four crosslinking reagents according to a procedure reported in our previous article. In this article, we report on the comprehensive evaluation of the swelling behavior of the prepared hydrogel membranes. These include the swelling kinetics, swelling behavior in terms of the pH and ionic strength of the swelling media, water absorbency under load (AUL), swelling as a function of sample size, deswelling behavior, and successive swelling and deswelling cycles. The swelling kinetics of the hydrogel membranes with higher crosslinking densities and lower swelling equilibria were closer to those of the case II transport mechanism; this is desirable in the field of drug-delivery systems (DDSs). Furthermore, higher crosslinking densities, and hence stronger structures, of the membranes led to higher AUL values and more stable performances in the successive swelling and deswelling cycles. Moreover, because of the anionic nature of the gum, the prepared GT hydrogels showed pH- and ionic-strength-dependent swelling behavior. All of these results reveal that GT could be a promising material for the preparation of hydrogel membranes for applications in the fields of DDS, tissue engineering, and the separation of small molecules. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2012