Structure-properties correlations in low-methylated pectin hydrogels and aerogels crosslinked by divalent ions

In this paper, structure-properties relationship between ionically crosslinked pectin hydrogels and aerogels is drawn, by focusing the study on the small amount of added cationic crosslinkers. Through this strategy and by coupling results from rheology and nanostructure of the gels provided by small-angle X-ray scattering, the early stages of the formation of ionic crosslinking junction zones are observed. Furthermore, as a major predictor of the samples' ability to resist linear shrinkage upon solvent exchange and supercritical drying processes, the gel-state (and thus rheological properties) emerges as a key element. Interestingly, after reaching a high enough crosslinking Ca²⁺-concentration to result in gelation, the average number of monomer segments between crosslinking points saturates as a function of Ca²⁺-concentration, while the size of the individual crosslinking junction zones continues to increase. When comparing the final characteristics of the supercritically-dried aerogels to these structural features of the cation-crosslinked hydrogels, crosslinking density of the hydrogels is observed to play a critical role.