Rheology and morphology of Pluronic F68 in water

Abstract

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.