A quantitative analysis of alginate swelling

The swelling behavior of physically cross-linked polysaccharides is not fully understood despite its significance in many applications such as drug delivery. In this study the swelling behavior of three types of alginate were characterized experimentally at various calcium concentrations. Additionally, equilibrium swelling data was analyzed in terms of Flory and rubber elasticity theories, which were developed for chemically cross-linked networks. This analysis suggested that these theories are not applicable for alginate. In particular, an increase in the number of monomeric units between cross-links was observed at a higher calcium concentration, whereas the theory predicts the opposite. The kinetics of the swelling process was also analyzed experimentally and theoretically. The experimental data was found to obey second-order kinetics. Moreover, a decrease in the swelling rate constant with elevated calcium concentration was observed. Lastly, it is indicated that the unusual swelling behavior of alginate could be attributed to a lateral chain association.