Water-responsive shape memory polyurethane block copolymer modified with polyhedral oligomeric silsesquioxane

Nanostructured polyurethane block copolymers with shape memory were synthesized by using polyhedral oligomeric silsesquioxane (POSS) molecules and poly(ethylene glycol) (PEG), which acted as the hydrophobic and hydrophilic groups, respectively. The hard segment domains appeared to be dominantly governed by POSS molecules according to X-ray diffraction and Fourier transform-infrared (FT-IR) measurements. As the POSS content increased, the phase separation between hard and soft segments gradually developed, followed by the crystallization of POSS molecules, and the melting temperature and heat of fusion for POSS crystals increased. The water-responsive shape memory behavior which resulted from the dissolution of soft segments was demonstrated at 30 degrees C. More than 70% shape recovery was achieved in the water-responsive shape recovery test, which depended on the POSS content.