Synthesis and Properties of Covalently Crosslinked Hydrogels Based on Arabinogalactan Polyaldehyde and Tartaric and Glutaric Dihydrazides

New hydrogels based on arabinogalactan polyaldehyde and glutaric and tartaric dihydrazides have been synthesized. Arabinogalactan polyaldehyde was synthesized via periodate oxidation and characterized by NMR, IR, and UV spectroscopy. The synthesis of hydrogels is based on a click reaction between the aldehyde groups of oxidized arabinogalactan and the amino groups of crosslinking agents, yielding Schiff bases in crosslinks. The effect of hydroxyl groups of the crosslinking agent on the properties of the resulting hydrogels was investigated. It was found that the hydrogels formed using glutaric dihydrazide, which does not contain hydroxyl groups, exhibit a lower elastic response in the frequency rheology test and lower shear modulus compared to hydrogels crosslinked with tartaric dihydrazide. The use of hydroxyl-containing tartaric dihydrazide as a crosslinking agent allows the synthesis of hydrogels with good mechanical properties and high hydrolytic stability in both neutral and acidic media. A distinctive feature of the hydrogels obtained is their resistance to swelling at various pH values, which decreases slightly after hydrogels treatment with sodium borohydride. The effect of arabinogalactan oxidation conditions on the properties of the hydrogels is also discussed.