Superabsorbent alginate aerogels

Polysaccharides are biopolymers that have excellent biocompatibility and biodegradability and have been considered for a wide range of pharmaceutical and biomedical applications. In this work polysaccharide-based superabsorbent aerogels are prepared using a combination of sol-gel and supercritical fluid technology. The advantages of supercritical drying are the reduced gel shrinkage, higher porosity, and three-dimensional network of the aerogel morphology compared to the morphology obtained with conventional air or vacuum drying methods. The aerogel open-porous structure and high surface area promotes rapid water absorption into the aerogel matrix by capillary force. Aerogel structural properties are modified by using different cross-linking ions and different alginate molecular weights and the influence of the aerogel properties on water absorption capacity is presented. Scanning electron microscopy is used to characterize the aerogel surface morphology, and nitrogen adsorption/desorption measurements are used to obtain information on the aerogel surface area, pore size, and pore volume. A unique feature of alginate aerogels is that they absorb more saline compared to distilled water, which is opposite to the behavior of regular superabsorbents. A gram of alginate aerogel absorbs as much as 120 g of saline (0.9 wt% aq. NaCl solution) solution compared to 20 g of distilled water. The results from these analytical methods highlight the improved product characteristics of the aerogels synthesized using sol–gel processing technology combined with supercritical fluid technology.