Gelation of mixed PEO–PPO–PEO copolymers in aqueous solution via mechanical spectroscopy

Gelation of concentrated aqueous solutions of Pluronic copolymers PE10100 (EO4PO53EO4), PE10500 (EO37PO56EO37), and their mixtures has been investigated by mechanical spectroscopy. With different PE10500/PE10100 weight ratios, a 20.0 wt% PE10500 aqueous solution exhibits a sol–gel transition at low temperature and a gel–sol transition at higher temperature even though no gelation was observed for the pure 20.0 wt% PE10500 solution itself. The two copolymers comicellize to give micelles with larger size, leading to gelation when the micellar volume fraction is above a critical value for hard-sphere interaction. Moreover, the gel region becomes broader as the proportion of PE10100 in the mixture is increased, due to the increased hydrophobicity of the solvent and the more PPO blocks available.