Cross-linked ionomeric materials from poly(styrene-alt-maleic anhydride) and poly(ethylene glycol) for biomedical applications: a preliminary investigation.

Two ionomeric materials, cross-linked through the formation of polyoxyethylene bridges, were synthesized by the reaction of poly(styrene-alt-maleic anhydride) (PSMA) with poly(ethylene glycol) (PEG), carried out in the absence of external catalysts. The reaction was carried out at room temperature, both in bulk with excess glycol, and in acetone solution with a 20:1 ratio of anhydride rings to hydroxyl groups. The materials were characterized by scanning electron microscopy (SEM), total reflection Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The SEM showed a quite uniform porous structure for the material synthesized in bulk, and two distinct phases for that synthesized in acetone solution, a sponge-like structure and a denser one. The FTIR spectra showed that the first material underwent the cross-linking reaction to a greater extent than the second one. Both TGA and DSC confirmed the formation of cross-linked structures. Such tri-dimensional networks, owing to the presence of the carboxyl groups, could easily entrap either cationic drugs, in view of a possible controlled release, or poisonous metal cations, when they must be removed from blood. The second use can be made easier by the hemocompatibility, ascertained in preceding studies on other materials, synthesized by the reaction between maleic anhydride copolymers and hydroxyl-containing macromolecules. Another possible use is the production of ion exchanging gels, as fillers for both ion exchange and liquid chromatography columns, which could be easily regenerated.