Preparation of water-soluble/insoluble derivatives of hyaluronic acid by cross-linking with epichlorohydrin in aqueous NaOH/NH4OH solution

In this study, the sorption isotherms of water vapor by chitosans with various molecular weights were measured. The BET adsorption theory was modified for the system that has several different kinds of energy levels in the water adsorption sites, i.e. a hydroxyl group, an amino group, the polymer chain end, etc. and applied it to the experimental results in order to examine the effect of the polymer chain end on the sorption isotherm of water¯chitosan using the parameters which represented the total number of adsorption sites, Vm, the interaction energy between water and the adsorption sites, K, and the number of adsorbed layers, n. Vm and K increased as the molecular weight decreased, and n remained constant. It has been proved that the increase in Vm and K were caused by the hydrophilic groups in the polymer chain end.