Linear poly(ethylene oxide)-based polyurethane hydrogels: polyurethane-ureas and polyurethane-amides

Over the last 30 years, water-swellable and water-insoluble hydrogels have been extensively investigated and developed, leading to a large family of m aterials which have found uses in a wide range of biomedical applications. While hydrogels usually present a crosslinked structure, linear polyurethan e-ureas (PUUs) based on poly(ethylene oxide) have been shown to be able to absorb and swell with aqueous media without dissolving. This behavior is du e to the phase separated domain morphology, where hydrogen bonded urethane/ urea hard segment domains are dispersed in a PEO soft segment domain. This work investigates the possibility of obtaining linear poly(ethylene ox ide)-based polyurethane-amide (PUA) hydrogels using two amide diols as chai n extenders, a mono amide diol (AD) and a diamide diol (DD), and a dicarbox ylic acid (maleic acid, MA). Poly(ethylene oxide) based PUAs were obtained using a "one-shot" bulk polymerization technique. The chemicophysical chara cterization and water-solubility tests showed that these materials, while h aving molecular weights similar to the PUUs, do not possess sufficient phas e separation, hydrogen bonding and hydrophobicity of the hard segment domai ns to exhibit hydrogel behavior. Crosslinked PUAs using maleic acid as chai n extender show interesting hydrogel properties. (C) 1999 Kluwer Academic P ublishers.