Liquid-to-solid transition in suspensions of swollen microgels

We investigate the phase and non-equilibrium behavior of suspensions comprised of swollen, ionic microgels as a function of particle stiffness. We find that stiff particles exhibit all three phases observed in hard sphere suspensions, liquid, crystal and glass. For particles with intermediate stiffness, the crystal phase disappears and the microgel suspension transitions from a liquid to a glassy state at certain particle concentration. For even softer particles, no glassy state is observed. Instead the system remains liquid within the experimentally accessed concentration range. Interestingly, for microgels with intermediate stiffness, we find that the bulk modulus of individual particles seems to control the mechanical properties of the microgel suspension in the overpacked regime, emphasizing the relevance of being compressible.