Ring-opening polymerization of epoxy end-terminated poly(ethylene oxide) as a route to highly crosslinked materials with exceptional swelling behavior (II)

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