Hybrid Hydrogels Obtained by the Copolymerization of Acrylamide with Aggregates of Methacryloyl Derivatives of Polyoxotungstates. A Comparison with Polyacrylamide Hydrogels with Trapped Aggregates

The synthesis and the swelling properties of two types of hybrid hydrogels have been studied to point out the contribution of cross-linking organic−inorganic aggregates to the network formation and the water absorption. The first type consists of polyacrylamide hydrogels with embedded polyoxotungstates. The second one has been obtained by radical polymerization of acrylamide in the presence of copolymerizable polyoxotungstates above their critical aggregation concentration. As recently reported for polyacrylamide hydrogels with trapped rods, the incorporation of such polyelectrolytes in a neutral network enhances the ability of the hydrogel to absord water. The same observation holds for polyacrylamide hydrogels with trapped polyoxotungstate aggregates. As polymerizable tetrafunctional polyoxotungstates and acrylamide were copolymerized, aggregate-containing hydrogels were obtained. Their swelling properties were found to be in the low range of those of superabsorbent materials and are discussed in relation to the presence of aggregated species.