Chitosan-xanthan gum PEC-based aerogels: A chemically stable PEC in scCO2

Abstract

An innovative aerogel obtained from a chitosan/xanthan gum polyelectrolyte complex (PEC) was developed in this work from the screening of thirteen different combinations of natural polyelectrolytes: two positively-charged biopolymers (chitosan and gelatin A), six negatively-charged biopolymers (pectin, iota-carrageenan, collagen, xanthan gum, alginate and modified galactomannan), and a neutral polymer (guar gum) using the statistical design of experiments (DOE) approach. Only the chitosan-xanthan gum formed aerogels under supercritical conditions using carbon dioxide at 150 bar and 250 bar and 35 °C. The chitosan-xanthan gum-based aerogels have bone-like structures and smooth surfaces, with pore size distributions in the meso- and macropore ranges, the average pore diameter of ∼20 nm and porosity between 60 and 70%. The specific surface areas of the aerogels processed at 150 bar and 250 bar are, respectively, 5.7 and 17.5 m2 g−1, values below those commonly reported in the literature for aerogels. The aerogels are thermally stable up to ∼240 °C, while the cryogel is thermally stable up to ∼224 °C. The value of the total weight loss through thermal decomposition of the aerogels (∼25%) is smaller than that of the cryogel (∼40%). These materials have potential applications in the environmental and biomedical areas, providing solutions to the current challenges in biomedicine and social, demographic and sanitary life sciences.