Nitrogen sorption as a tool for the characterisation of polysaccharide aerogels
Abstract
Supercritically dried aerogels of several polysaccharides (chitin, chitosan, alginate, alginic acid, k- carrageenan, and agar) have been characterised by physisorption ofN2. Surface areas as high as 570m2 g−1 have been measured. The nature of the functional groups of the polysaccharide significantly influences the adsorption of N2 on the surface of the aerogel. The net enthalpy of adsorption increases with the polarity of the surface groups of the polymer, in the order chitin < agar≤chitosan < carrageenan < alginic acid∼alginate. The surface area and the mesopore distribution of the aerogels depend both on the dispersion of the parent hydrogel and on the behaviour of each polymer in the drying treatment. Aerogels which retain the dispersion of the parent hydrogel are mainly macroporous (pores larger than 50 nm) while materials liable to shrink upon solvent exchange form mesoporous structures.
Keywords
adsorption enthalpy
surface polarity
comparison plots
Aerogel
supercritical drying
carrageenan
physisorption
polysaccharides
alginate
chitosan
chitin
agar
carrageenan.
Supercritical drying
Comparison plots
Surface polarity
Adsorption enthalpy
Physisorption
Polysaccharides
Alginate
Chitosan
Chitin
Agar
Carrageenan
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