Crossover behavior on temperature dependence of volume of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)–based hydrogels

We have investigated the temperature dependence of volume of hydrogels composed of a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-b-PPO-b-PPO) copolymer. Mechanical tests for the gels at various temperatures indicate that physical crosslinks are introduced into the gel systems around the critical micelle temperature for solutions of the triblock copolymer. The origin of the marked volume change for the PEO-b-PPO-b-PEO–based hydrogels can be explained by the crossover between the two states with and without aggregates of the PPO blocks.