Microstructure and Rheology of Thermoreversible Nanoemulsions

Thermoreversible nanoemulsions are technologically important materials that form gels with solid-like properties upon heating. Recently, we developed a model system using PDMS droplets suspended in a continuous phase consisting of cross-linkable poly(ethylene glycol) diacrylate and the surfactant sodium dodecyl sulfate [Helgeson, M.E. et al. Nature Materials (2012)]. Confocal microscopy experiments spanning a range of volume fractions show that the PDMS droplets form space-spanning structure that depend upon the difference in temperature from the gelation point. We compute the structure factor by applying a fast Fourier transform to the 2D images of the gels. Comparison with the temperature-dependent small amplitude oscillatory rheology show that the elastic moduli of the gels scale as a function of the characteristic length scales present within these gels.