Modelling of swelling of PVA hydrogels considering non-ideal mixing behaviour of PVA and water

Poly(vinyl alcohol) (PVA) hydrogel microbeads are widely used as embolization agents for the treatment of cancer in filtering organs. The success of embolization procedures depends strongly on the swelling properties of the hydrogels. PVA hydrogels can be understood as non-ideal mixtures of PVA and water. Here, the sum of PVA and water volumes is different from the volume of their resulting mixture. The correlation between volumetric and mass swelling of PVA and water is highly relevant to several technological issues. In the present contribution, the water uptake (WU), the most important characteristic of PVA hydrogel microbeads intended for use as embolic agents, was investigated considering the hydrogel as a non-ideal mixture of PVA and water. Hydrogel microbeads were obtained by chemical crosslinking of PVA with glutaraldehyde (GA) in an emulsion. The structure of the resulting microbeads was investigated using FT-IR, SEM and digital image analysis. The volumetric and mass swelling of the microbeads in water were followed by optical microscopy and gravimetric studies, respectively. Additionally, a WU model for hydrogels where the polymer and water behave as non-ideal mixtures is presented.