We report here studies directed toward the synthesis and characterization of cross-linked poly(ethylene oxide) gels for use as drug delivery platforms. These gels were prepared by anionic ringopening polymerization of diepoxy PEO 400, PEO3400, and PEO8000 using t-BuOK as the initiator. The diepoxy PEO3400 and PEO8000 derived gels were found to swell to 20× and 30× their initial masses in water, falling in the category of superadsorbants. Evaluation of their behavior as disintegrants using lactose and calcium phosphate, in comparison with commercial disintegrant croscarmellose sodium, showed the diepoxy PEO3400 gel to be twice as fast in disintegrating a tablet. The diepoxy PEO3400 and PEO8000 derived gels were characterized by XRD, DSC, and TGA. and compared with the linear versions of the same materials. XRD powder patterns for all materials are very similar, albeit those for the gels are less intense likely because of packing disorders near cross-links. DSC data indicate that both Tm and Tc are consistently lower by 5-10 °C in the cross-linked systems. The lower the Tm and Tc, the greater the degree of swelling. Although the PEO3400 gels swell less than the PEO8000 gels, they swell faster as judged by disintegrant studies. One interpretation of these results suggests a potential new mechanism for the design of hydrogels and superadsorbants wherein cross-linking creates higher energy forms than found in the linear polymers. Such higher energy forms would melt and crystallize at lower temperatures. Likewise higher energy forms would solvate and swell more rapidly.

Highly swellable poly(ethylene oxide) (PEO) gels were prepared by anionic ring‐opening polymerization of diepoxy end‐capped PEO (3400 g mol−1) and PEO (8000 g mol−1) using dianionic glycerol and glycolic acid initiators at scales of up to 50 g diepoxide. The glycerol‐derived materials swell to almost 20 times their mass in water. The driving force for rapid swelling appears to arise during ‘crystallization’, as segments between crosslinks are forced to pack under conditions that create high‐energy domains within the material. Solvation and therefore swelling are driven by the release of the resulting packing energy. These observations may offer insight into methods for designing other highly swellable materials. When the polyfunctional initiators have groups with different reactivities (e.g. alkoxide versus carboxylate), as might be expected, the more nucleophilic functional group appears to dominate the ring‐opening polymerization process. Copyright © 2007 Society of Chemical Industry