A SYNTHETIC HYDROGEL WITH THERMOREVERSIBLE GELATION .1. PREPARATION AND RHEOLOGICAL PROPERTIES

Block copolymers composed of poly(N-isopropylacrylamide-co-n-butyl met hacrylate) [poly(NIPAAm-co-BMA)] and poly(ethylene glycol) (PEG) were prepared. Aqueous solutions of the block copolymers were characterized by dynamic viscoelastic measurement as a function of temperature. The fluid solutions turned into hydrogels upon heating while keeping thei r transparency and without syneresis. The hydrogels turned back into s olutions upon cooling. The thermoreversible sol-gel transition was obs erved with no hysteresis. The sol-gel transition temperatures were clo sely correlated to the lower critical solution temperature of the poly (NIPAAm-co-BMA) in the block copolymers. Gelation is believed to be ca used by thermoreversible crosslinkages between intermolecular poly(NIP AAm-co-BMA) blocks due to hydrophobic interaction.