Glass-glass transition during aging of a colloidal clay

Recent advances in the study of soft materials have led in the last decades to a deeper knowledge of equilibrium and non-equilibrium states and to the discovery of new phases and transitions besides the ones commonly experienced in atomic or molecular systems. Among these glass-glass transitions are quite rare to be found, especially at ambient conditions. Here we report the evidence of a spontaneous glass-glass transition taking place during aging of a colloidal clay through a combination of dilution experiments, X-Ray Photon Correlation Spectroscopy, Small Angle X-ray Scattering and Monte Carlo simulations.