Rheology and morphology of Pluronic F68 in water

We investigated the morphological transitions of aqueous solutions of Pluronic F68 induced by temperature and polymer concentration by means of rheological and x-ray measurements. We adopted a rheological method to evaluate the characteristic equilibrium temperatures associated with the transition from unimers to spherical micelles and from disordered spherical micelles to a body-centered cubic phase. We used the transition temperatures to build the phase diagram water/F68. Based on a paracrystalline model for hard spheres, we extracted the characteristic size of the micellar core as a function of temperature from small-angle x-ray scattering (SAXS) data. We compared the microstructural information obtained via SAXS with the rheological response, and we developed a consistent link between the microstructural evolution of the system and the macroscopic flow properties.