We investigate by rheology and light scattering the influence of the elastic modulus, G(0), on the slow dynamics and the aging of a soft glass. We show that the slow dynamics and the aging can be entirely described by the evolution of an effective viscosity, eta(eff), defined as the characteristic time measured in a stress relaxation experiment times G(0). At all times, eta(eff) is found to be independent of G(0), of elastic perturbations, and of the rate at which the sample is quenched in the glassy phase. We propose a simple model that links eta(eff) to the internal stress built up at the fluid-to-solid transition.

We report the preparation of direct hexagonal liquid crystals, constituted of oil-swollen cylinders arranged on a triangular lattice in water. The volume ratio of oil over water, ρ, can be as large as 3.8. From the lattice parameter measured by small-angle X-ray scattering, we show that all the oil is indeed incorporated into the cylinders, thus allowing the diameter of the cylinders to be controlled over one decade range, provided that the ionic strength of the aqueous medium and ρ are varied concomitantly. These hexagonal swollen liquid crystals (SLCs) have been first reported with sodium dodecyl sulfate as anionic surfactant, cyclohexane as solvent, 1-pentanol as co-surfactant, and sodium chloride as salt (Ramos, L.; Fabre, P. Langmuir 1997, 13, 13). The stability of these liquid crystals is investigated when the pH of the aqueous medium or the chemical nature of the components (salt and surfactant) is changed. We demonstrate that the range of stability is quite extended, rendering swollen hexagonal phases potentially useful for the fabrication of nanomaterials. As illustrations, we finally show that gelation of inorganic particles in the continuous aqueous medium of a SLC and polymerization within the oil-swollen cylinders of a SLC can be conducted without disrupting the hexagonal order of the system.

Fluorescence recovery after pattern photobleaching is used to measure the self-diffusion of surfactant molecules, along cylinders and perpendicular to their main axis in an oriented hexagonal lyotropic phase. Unexpectedly, while the motion along cylinders is diffusive, a superdiffusive behavior is observed in the direction perpendicular to the cylinder axis. Moreover, varying the lattice parameter, we found that the perpendicular diffusion time is governed only by the number of cylinders to cross, providing experimental evidence for superdiffusion with a bounded step length.

Measuring, characterizing and modelling the slow dynamics of glassy soft matter is a great challenge, with an impact that ranges from industrial applications to fundamental issues in modern statistical physics, such as the glass transition and the description of out-of-equilibrium systems. Although our understanding of these phenomena is still far from complete, recent simulations and novel theoretical approaches and experimental methods have shed new light on the dynamics of soft glassy materials. In this paper, we review the work of the last few years, with an emphasis on experiments in four distinct and yet related areas: the existence of two different glass states (attractive and repulsive), the dynamics of systems very far from equilibrium, the effect of an external perturbation on glassy materials, and dynamical heterogeneity.