Understanding the Swelling Behavior of Polysaccharide-Based Hydrogels through a Kinetic Modeling

Hydrogels are versatile polymeric materials widely used in various applications, including drug delivery, agriculture, and environmental technologies. Their performance and applicability are mainly governed by the swelling behavior. As a result, an accurate description of swelling kinetics is crucial for understanding the transport mechanisms that guide the hydrogel design. However, the power-law model fails to describe the full swelling profile and transient phenomena, such as, nonmonotonic swelling. In this work, we propose a physical model based on a kinetic interpretation, which is capable of describing the entire swelling profile of hydrogels. The model is derived from fundamental transport concepts, and incorporates both Fickian diffusion and macromolecular relaxation within a unified framework. Importantly, several classical swelling equationsincluding the power law, first-order kinetic, Peppas-Sahlin, and Higuchi modelsare shown to emerge as particular cases of the proposed formulation. The model was validated using experimental swelling data of chemically cross-linked polysaccharide-based hydrogels with different compositions. The proposed equation accurately fitted the swelling curves, including the overshooting behavior, with high correlation coefficients. The model quantified the contribution of Fickian diffusion and macromolecular relaxation in the swelling mechanism. The proposed model offers a simple and comprehensive tool for analyzing hydrogel swelling kinetics. By describing the full swelling process with only three physical parameters, it enables improved mechanistic interpretation, providing valuable guidance for the rational design of hydrogels with tailored swelling and absorption properties.