Binodal and spinodal curves of an L3 (sponge) phase

Abstract

In a previous paper (T. D. Le, U. Olsson, H. Wennerström and P. Schurtenberger, Phys. Re. E, 1999, 60, 4300) we presented a quantitative thermodynamic analysis of an L₃ (sponge) phase formed in the C₁₂E₅–n-decane–water system where the focus was on the narrow stability range of the phase. In this study, we continue to develop and test the free energy model used in that analysis by extending the light scattering measurements towards the two-phase region. This is done by using the Joule heating temperature jump (JHTJ) technique to instantaneously jump (microsecond pulse) from an equilibrium state to a metastable state at a higher temperature. With multiple photosensors placed around the sample, we simultaneously measured the relaxation of the scattered light intensity at different scattering vectors, q. Our best-stretch of this set-up yielded a data set containing the q-dependent scattered intensity and turbidity measurements for a broad range of temperatures and concentrations. The combined phase equilibrium and T-jump data set shows agreement between experimental and theoretical binodal and spinodal curves of this L₃ phase.