Structure and properties of urea-crosslinked star poly[(ethylene oxide)-ran-(propylene oxide)] hydrogels.

Isocyanate-terminated six armed star shaped macromers with a statistical copolymer backbone consisting of 80% EO and 20% PO have previously demonstrated excellent protein and cell repellence as nano-layered surfaces. In this study, various macromers are mixed with water and provide a spectrum of materials that range from particles to uniform hydrogels. Due to hydrophobic end groups, 3 kDa molecular weight macromers result in micro and nano-particles, while 18 kDa macromers completely dissolve and consequently uniform, transparent, high water content hydrogels are formed. Oriented channels may be induced into these hydrogels through the controlled freezing of water in the preformed hydrogel.