SWELLING PROPERTIES OF HYALURONIC-ACID ESTER MEMBRANES

Swelling equilibrium and kinetics of swelling for hyaluronic acid (HA) benzyl ester membranes were examined in media of different pH and ion ic strength, and for varying percent esterification of the polymers. T he equilibrium swelling properties for polymers with an intermediate ( 75-85%) degree of esterification in different media can be explained b y the Donnan equilibrium theory. However, this theory does not apply t o the swelling behaviors of membranes with high (> 85%) and low (< 75% ) degrees of esterification, implying that non-ideal conditions must a lso be considered. The kinetics of swelling in media of different ioni c strength can be described by a second-order swelling model, with bot h diffusion and stress relaxation contributing to the process. Ion exc hange influences the swelling kinetics of HA ester membranes at lower pH in the medium.