Glass transition and aging in dense suspensions of thermosensitive microgel particles.

We report a thermosensitive microgel suspension that can be tuned reversibly between the glass state at low temperature and the liquid state at high temperature. Unlike hard spheres, we find that the glass transition for these suspensions is governed by both the volume fraction and the softness of the particles, where softer suspensions form a glass at higher effective volume fractions. In the glass state, these suspensions show aging where the relaxation times increase linearly with age, irrespective of the degree of particle softness. This relaxation scaling is in contrast with hard sphere behavior but consistent with the soft glassy rheology model.