Softness mapping of the concentration dependence of the dynamics in model soft colloidal systems

Transition in the Glassy Dynamics of Melts of Acid-Hydrolyzed Phytoglycogen Nanoparticles

“…Dispersions of rigid, moderately polydisperse, incompressible hard-sphere colloids that interact strictly through excluded volume interactions exhibit a hard-sphere glass transition at a volume fraction ϕ = ϕ g, HS = 0.58, which is slightly less than that of random close packing of the particles, ϕ rcp = 0.64. , In contrast, concentrated dispersions of soft colloidal particles such as liposomes, , polymeric nanocapsules, and microgels − can have much more complex behavior. Deformation, interpenetration, and deswelling of soft particles can occur at high packing densities, so that it is practical to define a generalized or effective volume fraction, ϕ eff , that does not account for changes in the particle volume: ϕ eff = nV o , where n is the particle number density and V o is the volume of an isolated, fully swollen particle in the limit n → 0. , The increase in the viscosity of soft-sphere dispersions with increasing ϕ eff is more gradual than that for hard-sphere dispersions, and the soft colloidal glass transition ϕ g is shifted to ϕ eff values that are larger than ϕ g, HS and ϕ rcp . ,, Considerable effort has been devoted to understanding soft colloidal glasses, and this has provided considerable insight into glassy dynamics, − aging, − and the connection between softness and fragility. , However, there remain many unanswered questions, and a complete understanding of the soft colloidal glass phase remains a considerable challenge, in large part due to the difficulty in measuring the ultraslow glassy particle dynamics on timescales accessible in experiments.…”