Chiral betulin-imino-chitosan hydrogels by dynamic covalent sonochemistry

A series of chiral hydrogels was prepared from a homogeneous mixture of chitosan and betulinic aldehyde in different molar ratios, under the effect of ultrasound. The hydrogelation mechanism has been investigated by FTIR and CD spectroscopy, wide angle X-ray diffraction and polarized light microscopy. The morphology of hydrogels was examined by SEM. The swelling ability has been tested in three media of different pH. It was concluded that hydrogelation occurred by different pathways, closely related to the peculiarities of the chitosan-betulin systems. Circular dichroism measurements revealed chiroptical properties of the hydrogels, correlated to their content and crosslinking pathway.