Preparation and properties of hydrogels based on hemicellulose

Xylan with glucuronic acid functionalities, separated from birchwood, was converted into hydrogels by dissolving it together with chitosan in acidic conditions. The hydrogels were formed at certain xylan/chitosan compositions. The mechanism of the gel formation was investigated with FTIR. Complexation between glucuronic acid functionalities of xylan and amino groups of chitosan is suggested to be responsible for network formation. The swelling behavior of these hydrogels was studied at various pH levels and salt concentrations, and the hydrogels responded in a reversible manner to various stimuli. DMA of the films showed separated transitions that may correspond to different phases. Imaging with AFM in TappingMode™ of the surfaces indicated discrete xylan and chitosan phases. A sponge-like microporous structure, as shown with SEM, was formed when a hydrogel was freeze dried.